Oracle® TimesTen Application-Tier Database Cache

User's Guide

11g Release 2 (11.2.2)

E21634-12

October 2014

Oracle TimesTen Application-Tier Database Cache User's Guide, 11g Release 2 (11.2.2)

E21634-12

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Contents

Preface

- Audience

- Related documents

- Conventions

- Documentation Accessibility

What's New

- New features in Release 11.2.2.7.0

- New features in Release 11.2.2.6.0

- New features in Release 11.2.2.5.0

- New features in Release 11.2.2.4.0

- New features in Release 11.2.2.2.0

- New features in Release 11.2.2.1.0

- New features in Release 11.2.2.0.0

1 TimesTen Application-Tier Database Cache Concepts

- Data management design

- Overview of a cache grid

- Overview of cache groups

- Cache instance

- Cache group types

- Transmitting updates between the TimesTen and Oracle databases

- Loading data into a cache group: Explicitly loaded and dynamic cache groups

- Sharing data across a cache grid: Local and global cache groups

- Summary of cache group types

- High availability caching solution

2 Getting Started

- Setting up the Oracle Database and TimesTen systems

- Create users in the Oracle database

- Create a DSN for the TimesTen database

- Create users in the TimesTen database

- Set the cache administration user name and password in the TimesTen database

- Creating a cache grid

- Creating cache groups

- Create the Oracle Database tables to be cached

- Start the cache agent

- Create the cache groups

- Start the replication agent for the AWT cache group

- Attaching the TimesTen database to the cache grid

- Performing operations on the read-only cache group

- Manually load the cache group

- Update the cached Oracle Database table

- Performing operations on the dynamic updatable global cache group

- Dynamically load the cache group

- Update the TimesTen cache table

- Cleaning up the TimesTen and Oracle Database systems

- Detach the TimesTen database from the cache grid

- Stop the replication agent

- Drop the cache groups

- Destroy the cache grid

- Stop the cache agent and destroy the TimesTen database

- Drop the Oracle Database users and their objects

3 Setting Up a Caching Infrastructure

- Configuring your system to cache Oracle Database data in TimesTen

- TimesTen Application-Tier Database Cache environment variables for UNIX

- TimesTen Application-Tier Database Cache environment variables for Microsoft Windows

- Configuring the Oracle database to cache data in TimesTen

- Create the Oracle database users

- Grant privileges to the Oracle database users

- Automatically create Oracle Database objects used to manage data caching

- Manually create Oracle Database objects used to manage data caching

- Configuring a TimesTen database to cache Oracle Database data

- Define a DSN for the TimesTen database

- Create the TimesTen users

- Grant privileges to the TimesTen users

- Set the cache administration user name and password

- Configuring data management

- Managing data locally

- Configuring a cache grid

- Modify the PROCESSES system parameter for ten or more grid nodes

- Create a cache grid

- Associate a TimesTen database with a cache grid

- Testing the connectivity between the TimesTen and Oracle databases

- Managing the cache agent

- Set a cache agent start policy

4 Defining Cache Groups

- Cache groups and cache tables

- Single-table cache group

- Multiple-table cache group

- Creating a cache group

- Read-only cache group

- Restrictions with read-only cache groups

- Asynchronous writethrough (AWT) cache group

- Managing the replication agent

- Configuring parallel propagation to Oracle Database tables

- What an AWT cache group does and does not guarantee

- Restrictions with AWT cache groups

- Reporting Oracle Database permanent errors for AWT cache groups

- Synchronous writethrough (SWT) cache group

- Restrictions with SWT cache groups

- User managed cache group

- READONLY cache table attribute

- PROPAGATE cache table attribute

- Examples of user managed cache groups

- AUTOREFRESH cache group attribute

- Altering a cache group to change the AUTOREFRESH mode, interval or state

- Manually creating Oracle Database objects for autorefresh cache groups

- Using a WHERE clause

- Proper placement of WHERE clause in a CREATE CACHE GROUP statement

- Referencing Oracle Database PL/SQL functions in a WHERE clause

- ON DELETE CASCADE cache table attribute

- UNIQUE HASH ON cache table attribute

- Caching Oracle Database synonyms

- Caching Oracle Database LOB data

- Implementing aging in a cache group

- LRU aging

- Time-based aging

- Manually scheduling an aging process

- Configuring a sliding window

- Dynamic cache groups

- Global cache groups

- Dynamic global cache groups

- Explicitly loaded global cache groups

- Start the replication agent

- Attach a TimesTen database to a cache grid

5 Cache Group Operations

- Transmitting updates between the TimesTen and Oracle databases

- Loading and refreshing a cache group

- Loading and refreshing an explicitly loaded cache group with autorefresh

- Loading and refreshing a dynamic cache group with autorefresh

- Loading and refreshing a cache group using a WITH ID clause

- Initiating an immediate autorefresh

- Loading and refreshing a multiple-table cache group

- Improving the performance of loading or refreshing a large number of cache instances

- Example of manually loading and refreshing an explicitly loaded cache group

- Example of manually loading and refreshing a dynamic cache group

- Dynamically loading a cache instance

- Dynamic load configuration

- Dynamic load guidelines

- Examples of dynamically loading a cache instance

- Return dynamic load errors

- Flushing a user managed cache group

- Unloading a cache group

- Unloading a cache group across all grid members

- Determining the number of cache instances affected by an operation

- Setting a passthrough level

- PassThrough=0

- PassThrough=1

- PassThrough=2

- PassThrough=3

- PassThrough=4

- PassThrough=5

- Considerations for using passthrough

- Changing the passthrough level for a connection or transaction

6 Creating Other Cache Grid Members

- Creating and configuring a subsequent standalone TimesTen database

- Replicating cache tables

- Create and configure the active database

- Create and configure the standby database

- Create and configure the read-only subscriber database

- Example of data sharing among the grid members

- Performing global queries on a cache grid

- Performing global queries with local joins

- Obtaining information about the location of data in the cache grid

- Adding other elements to a cache grid or grid member

7 Managing a Caching Environment

- Checking the status of the cache and replication agents

- Cache agent and replication connections

- Monitoring cache groups and cache grids

- Using the ttIsql utility's cachegroups command

- Monitoring autorefresh operations on cache groups

- Monitoring AWT cache groups

- Configuring a transaction log file threshold for AWT cache groups

- Obtaining information for a cache grid

- Suspending global AWT cache group operations

- Tracking DDL statements issued on cached Oracle Database tables

- Managing a caching environment with Oracle Database objects

- Impact of failed autorefresh operations on TimesTen databases

- Dropping Oracle Database objects used by autorefresh cache groups

- Monitoring the cache administration user's tablespace

- Defragmenting change log tables in the tablespace

- Manually defragmenting the change log tables for autorefresh cache groups

- Receiving notification on tablespace usage

- Recovering from a full tablespace

- Recovering after failure of a grid node

- Backing up and restoring a database with cache groups

- Backing up and restoring using the ttBackup and ttRestore utilities

- Backing up and restoring with the ttMigrate utility

- Changing cache user names and passwords

8 Cache Performance

- Dynamic load performance

- Improving AWT throughput

- Improving AWT throughput with parallel propagation

- Improving AWT throughput with SQL array execution

- Improving performance when using incremental autorefresh for read-only cache groups

- Improving execution of large transactions when using incremental autorefresh for read-only cache groups

- Using ttCacheAutorefreshXactLimit

- Example of potential transactional inconsistency

- Retrieving statistics to evaluate performance when a transaction limit is set

- Configuring a select limit when using incremental autorefresh for read-only cache groups

- How to determine the cache group name for a particular select limit

- Retrieving statistics to evaluate performance when using a select limit

- Improving performance when reclaiming memory during autorefresh operations

- Retrieving statistics on autorefresh transactions

- Caching the same Oracle table on two or more TimesTen databases

9 Cleaning up the Caching Environment

- Detaching a TimesTen database from a cache grid

- Stopping the replication agent

- Dropping a cache group

- Destroying a cache grid

- Stopping the cache agent

- Destroying the TimesTen databases

- Dropping Oracle Database users and objects

- Recommended method for a scheduled shutdown of an active standby pair with AWT cache groups

10 Using the Cache Advisor

- Cache Advisor overview

- Setting up the Oracle Database and TimesTen host systems

- Configure the target Oracle database

- Configure the repository Oracle database

- Configure the TimesTen database

- Cache Advisor configuration options and usage guidelines

- Supported configuration options for hosts and databases

- Restrictions and assumptions

- Running a SQL workload application

- Running the Cache Advisor

- Improve performance by using NFS or FTP for transferring data

- Viewing the Cache Advisor reports

- Cleaning up the Oracle and TimesTen databases and host systems

- Clean up the target Oracle database and host system

- Clean up the repository Oracle database and host system

- Clean up the TimesTen database and host system

11 Using TimesTen Application-Tier Database Cache in an Oracle RAC Environment

- How TimesTen Cache works in an Oracle RAC environment

- Restrictions on using TimesTen Cache in an Oracle RAC environment

- Setting up TimesTen Cache in an Oracle RAC environment

12 Using TimesTen Application-Tier Database Cache with Data Guard

- Components of MAA for TimesTen Application-Tier Database Cache

- How TimesTen Cache works with Data Guard

- Configuring the Oracle databases

- Configuring the TimesTen database

A Procedure and Privileges for Caching Oracle Database Data in TimesTen

- Quick reference to cache Oracle Database data in TimesTen

- Required privileges for the cache administration user and the cache manager user

B SQL*Plus Scripts for TimesTen Application-Tier Database Cache

- Installed SQL*Plus scripts

C Compatibility Between TimesTen and Oracle Databases

- Summary of compatibility issues

- Transaction semantics

- API compatibility

- SQL compatibility

- Schema objects

- Caching Oracle Database partitioned tables

- Nonschema objects

- Differences between Oracle Database and TimesTen tables

- Data type support

- SQL operators

- SELECT statements

- SQL subqueries

- SQL functions

- SQL expressions

- INSERT/DELETE/UPDATE/MERGE statements

- TimesTen-only SQL and built-in procedures

- PL/SQL constructs

- Mappings between Oracle Database and TimesTen data types

Glossary

Index

Preface

Oracle TimesTen In-Memory Database (TimesTen) is a relational database that is memory-optimized for fast response and throughput. The database resides entirely in memory at run time and is persisted to disk storage for the ability to recover and restart. Replication features allow high availability. TimesTen supports standard application interfaces JDBC, ODBC, and ODP.NET, in addition to Oracle interfaces PL/SQL, OCI, and Pro*C/C++. TimesTen is available separately or as a cache for Oracle Database.

TimesTen Application-Tier Database Cache is an Oracle Database product option that is ideal for caching performance-critical subsets of an Oracle database into cache tables within TimesTen databases for improved response time in the application tier. Cache tables can be read-only or updatable. Applications read and update the cache tables using standard Structured Query Language (SQL) while data synchronization between the TimesTen database and the Oracle database is performed automatically.

TimesTen Application-Tier Database Cache offers applications the full generality and functionality of a relational database, the transparent maintenance of cache consistency with the Oracle database, and the real-time performance of an in-memory database.

Audience

This guide is for application developers who use and administer TimesTen, and for system administrators who configure and manage TimesTen databases that cache data from Oracle databases. To work with this guide, you should understand how relational database systems work. You should also have knowledge of SQL, and either Open Database Connectivity (ODBC), Java Database Connectivity (JDBC), or Oracle Call Interface (OCI).

Related documents

TimesTen documentation is available on the product distribution media and on the Oracle Technology Network (OTN):

http://www.oracle.com/technetwork/database/database-technologies/timesten/documentation/index.html

Oracle Database documentation is also available on the Oracle Technology network. This may be especially useful for Oracle Database features that TimesTen supports, but does not document.

http://www.oracle.com/pls/db112/homepage/

Conventions

TimesTen supports multiple platforms. Unless otherwise indicated, the information in this guide applies to all supported platforms. The term Windows refers to all supported Windows platforms. The term UNIX applies to all supported UNIX and Linux platforms. See "Platforms" in Oracle TimesTen In-Memory Database Release Notes for specific platform versions supported by TimesTen.

Note:
In TimesTen documentation, the terms "data store" and "database" are equivalent. Both terms refer to the TimesTen database.

This document uses the following text conventions:

Convention

Meaning

boldface

Boldface type indicates graphical user interface elements associated with an action, or terms defined in text.

italic

Italic type indicates book titles, emphasis, or placeholder variables for which you supply particular values.

monospace

Monospace type indicates commands within a paragraph, URLs, code in examples, text that appears on the screen, or text that you enter.

italic monospace

Italic monospace type indicates a variable in a code example that you must replace. For example:
Driver=TimesTen_install_dir/lib/libtten.so

Replace TimesTen_install_dir with the path of your TimesTen installation directory.

[ ]

Square brackets indicate that an item in a command line is optional.

{ }

Curly braces indicate that you must choose one of the items separated by a vertical bar ( | ) in a command line.

|

A vertical bar separates alternative arguments.

. . .

An ellipsis (. . .) after an argument indicates that you may use more than one argument on a single command line.

%

The percent sign indicates the UNIX shell prompt.

#

The number (or pound) sign indicates the prompt for the UNIX root user.

TimesTen documentation uses these variables to identify path, file and user names:

Convention

Meaning

TimesTen_install_dir

The path that represents the directory where the current release of TimesTen is installed.

TTinstance

The instance name for your specific installation of TimesTen. Each installation of TimesTen must be identified at install time with a unique alphanumeric instance name. This name appears in the install path.

bits or bb

Two digits, 32 or 64, that represent either the 32-bit or 64-bit version of the operating system.

release or rr

The first three parts in a release number, with or without dots. The first three parts of a release number represent a major TimesTen release. For example, 1122 or 11.2.2 represents TimesTen 11g Release 2 (11.2.2).

jdk_version

One or two digits that represent the major version number of the Java Development Kit (JDK) release. For example, 5 represents JDK 5.

DSN

The data source name.

Documentation Accessibility

For information about Oracle's commitment to accessibility, visit the Oracle Accessibility Program website at http://www.oracle.com/pls/topic/lookup?ctx=acc&id=docacc.

Access to Oracle Support

Oracle customers have access to electronic support through My Oracle Support. For information, visit http://www.oracle.com/pls/topic/lookup?ctx=acc&id=info or visit http://www.oracle.com/pls/topic/lookup?ctx=acc&id=trs if you are hearing impaired.

What's New

This section summarizes the new features of TimesTen Application-Tier Database Cache release 11.2.2 that are documented in this guide and provides links to more information.

New features in Release 11.2.2.7.0

- The Oracle In-Memory Database Cache is now named the Oracle TimesTen Application-Tier Database Cache. Previous references to "IMDB Cache" are now referenced as "TimesTen Cache."

New features in Release 11.2.2.6.0

- You can manage the size of the reclaim buffer for the cache agent used to process autorefresh. You can also manage the size of the reclaim buffer for the replication agent when using an active standby pair replication scheme that includes autorefresh cache groups. See "Improving performance when reclaiming memory during autorefresh operations."

New features in Release 11.2.2.5.0

- UNLOAD CACHE GROUP now supports the COMMIT EVERY n ROWS clause to specify a commit frequency. See "Unloading a cache group". However, if you use this clause, the unload operation does not execute across grid members. For details, see "Unloading a cache group across all grid members".

- If you are using parallel propagation for AWT cache groups, any missing unique index, unique constraint, or foreign key constraint on the columns of the cached Oracle Database tables cause the propagation of transactions to be serialized to the Oracle database. See "Table constraint restrictions when using parallel propagation for AWT cache groups".

- Prolonged use or a heavy workload of the change log tables can result in fragmentation of the tablespace. In order to prevent degradation of the tablespace from fragmentation of the change log tables, TimesTen calculates the fragmentation for the tablespace and provides a way to defragment the tablespace and reclaim the space. For more details, see "Defragmenting change log tables in the tablespace".

- Oracle Database permanent errors logged to the awterrs text file can now also be written in XML format. For more details, see "Reporting Oracle Database permanent errors for AWT cache groups".

- At certain times, you may execute large transactions, such as for the end of the month, the end of a quarter, or the end of the year transactions. You may also have situations where you modify or add a large amount of data in the Oracle database over a short period of time. For read-only, autorefresh cache groups, TimesTen could potentially run out of permanent space when an autorefresh operation applies either one of these cases. Therefore, for these situations, you can configure an autorefresh transaction limit, where the large amount of data is broken up, applied, and committed over several smaller transactions. For details, see "Improving execution of large transactions when using incremental autorefresh for read-only cache groups".

- You can now set the value for the CacheAWTMethod first connection attribute with the ttDBConfig built-in procedure. See "Improving AWT throughput".

- When using AWT cache groups, you can use parallel propagation for AWT cache groups that batches together one or more transactions to be applied in parallel to the back-end Oracle database. The CacheParAwtBatchSize parameter configures a threshold value for the number of rows included in a single batch. See "Configuring batch size for parallel propagation for AWT cache groups".

- There are now a set of recommended steps when scheduling a shutdown of an active standby replication pair with AWT cache groups. For more information, see "Recommended method for a scheduled shutdown of an active standby pair with AWT cache groups".

- You can perform a dynamic load for queries with equality conditions on all columns in primary keys, with equality conditions on all columns in unique indexes, or with a mixture of equality or IS NULL conditions on all columns in unique indexes (provided that at least one equality condition is used). For more details, see "Dynamically loading a cache instance".

- You can manually initiate a check for missing constraints for AWT cache groups with the ttCacheCheck built-in procedure. After any schema change on the Oracle database, you should perform an manual check for missing constraints by executing ttCacheCheck on the TimesTen database. See "Manually initiate check for missing constraints".

New features in Release 11.2.2.4.0

- New instructions have been added on how to backup and restore a TimesTen database that contains one or more cache groups. For more details, see "Backing up and restoring a database with cache groups".

- A new tool, the TimesTen Cache Advisor, enables Oracle Database customers to determine whether the performance of an existing Oracle Database application can be improved if the application is used with TimesTen Cache. Cache Advisor generates recommendations of TimesTen cache group definitions based on the SQL usage in the Oracle Database application. For more information, see Chapter 10, "Using the Cache Advisor".

New features in Release 11.2.2.2.0

- You can configure parallel propagation of changes in AWT cache tables to the corresponding Oracle Database tables using either the ReplicationParallelism or CacheAWTParallelism data store attributes. See "Configuring parallel propagation to Oracle Database tables".

- If you are using parallel propagation, any unique index, unique constraint, or foreign key constraint on the columns of the cached tables in the Oracle Database must also be created on the cached tables in the AWT cache group. See "Configuring parallel propagation to Oracle Database tables".

New features in Release 11.2.2.1.0

- You can configure parallel propagation of changes in AWT cache tables to the corresponding Oracle Database tables. See "Configuring parallel propagation to Oracle Database tables".

- The default value for the CacheAWTMethod first connection attribute has changed. See "Improving AWT throughput".

New features in Release 11.2.2.0.0

- You can obtain information about the grid node where a global query is being executed. See "Obtaining information about the location of data in the cache grid".

- You can perform a local join when executing a global query. See "Performing global queries with local joins".

1 TimesTen Application-Tier Database Cache Concepts

TimesTen Application-Tier Database Cache is an Oracle Database product option that includes the Oracle TimesTen In-Memory Database. It is used as a database cache at the application tier to cache Oracle Database data and reduce the workload on the Oracle database. It also provides the connection and transfer of data between an Oracle database and a TimesTen database, as well as facilitating the capture and processing of high-volume event flows into a TimesTen database and subsequent transfer of data into an Oracle database.

You can cache Oracle Database data in a TimesTen database within cache groups. A cache group in a TimesTen database can cache a single Oracle Database table or a group of related Oracle Database tables. You can also share Oracle Database data globally across several TimesTen databases with global cache groups, which must be members of a cache grid.

This chapter includes the following topics:

- Data management design

- Overview of cache groups

- High availability caching solution

Data management design

When designing how you will use the TimesTen in-memory database, you must initially choose from the following:

- Manage data locally, where each TimesTen in-memory database operates separately from other TimesTen in-memory databases. This option is simpler than when managing global data; however, TimesTen does not manage data coherence across all TimesTen in-memory databases. For more details, see "Managing data locally".

- Manage data globally across multiple TimesTen in-memory databases with a cache grid. This is the default method. A cache grid is a collection of TimesTen Cache databases that collectively manage application data located within global cache groups. A cache grid contains a set of distributed TimesTen in-memory databases that work together to cache data from an Oracle database and guarantee cache coherence for global cache groups located on these TimesTen databases. See "Overview of a cache grid" for more information.

Overview of a cache grid

A cache grid is a set of distributed TimesTen in-memory databases that work together to cache data from an Oracle database and guarantee cache coherence for global cache groups among the TimesTen databases. Use a cache grid only if you plan on using global cache groups.

A grid consists of one or more in-memory database grid members that collectively manage the application data using the relational data model. The members of a grid cache data from a single Oracle database. A grid member can be either a standalone TimesTen database or an active standby pair.

A grid node is the database for a grid member. A node is one of the following:

- A standalone TimesTen database

- The active master database in an active standby pair

- The standby master database in an active standby pair

Thus, a grid member that is a standalone database consists of one node. A grid member that is an active standby pair consists of two nodes.

Figure 1-1 shows a cache grid containing three members: two standalone TimesTen databases and an active standby pair. The grid has four nodes: the two standalone TimesTen databases, the active master database and the standby master database of the active standby pair. The read-only subscriber database is not part of the cache grid because it has no connectivity with the Oracle database. The read-only subscriber receives replicated updates from the standby master database.

Figure 1-1 Cache grid with three grid members caching data from an Oracle database

In a cache grid, global cached data is dynamically distributed across multiple grid members without shared storage. This architecture enables the capacity of the cache grid to scale based on the processing needs of the application. When the workload increases or decreases, new grid members attach to the grid or existing grid members detach from the grid. Attaching to or detaching from the grid are online operations that do not interrupt operations on other grid members.

When requests are submitted to the grid members, the cache grid automatically redistributes data based on application access patterns. The location of the data is transparent to the application, but the cache grid redistributes data dynamically to minimize access time. The cache grid automatically maintains cache coherence and transactional consistency across the grid members. You can also configure the cache grid to perform global queries without redistributing the data. See "Performing global queries on a cache grid".

TimesTen databases within a cache grid can contain explicitly loaded and dynamic cache groups, as well as local and global cache groups of any cache group type that is supported for the various cache group classifications and categories. Although cache coherence is only managed for global cache groups.

See "Cache group types" for details about the different types of cache groups.

See "Loading data into a cache group: Explicitly loaded and dynamic cache groups" for details about the differences between an explicitly loaded and a dynamic cache group.

See "Sharing data across a cache grid: Local and global cache groups" for details about the differences between a local and a global cache group.

See "Configuring a cache grid" for information about creating a cache grid and associating a TimesTen database with a cache grid.

Overview of cache groups

Cache groups define the Oracle Database data to be cached in a TimesTen database. A cache group can be defined to cache all or part of a single Oracle Database table, or a set of related Oracle Database tables.

Figure 1-2 shows the target_customers cache group that caches a subset of a single Oracle Database table customer.

Figure 1-2 Single-table cache group

You can cache multiple Oracle Database tables in the same cache group by defining a root table and one or more child tables. A cache group can contain only one root table.

In a cache group with multiple tables, each child table must reference the root table or another child table in the same cache group using a foreign key constraint. Although tables in a multiple-table cache group must be related to each other in the TimesTen database through foreign key constraints, the corresponding tables do not necessarily need to be related to each other in the Oracle database. The root table does not reference any table with a foreign key constraint. See "Multiple-table cache group" for more details about the characteristics of a multiple-table cache group.

Cache instance

Data is loaded from an Oracle database into a cache group within a TimesTen database in units called cache instances. A cache instance is defined as a single row in the cache group's root table together with the set of related rows in the child tables.

Figure 1-3 shows three tables in the customer_orders cache group. The root table is customer. orders and order_item are child tables. The cache instance identified by the row with the value 122 in the cust_num primary key column of the customer table includes:

- The two rows with the value 122 in the cust_num column of the orders table (whose value in the ord_num primary key column is 44325 or 65432), and

- The three rows with the value 44325 or 65432 in the ord_num column of the order_item table

Figure 1-3 Multiple-table cache group

Cache group types

The most commonly used types of cache groups are:

- Read-only cache group
A read-only cache group enforces a caching behavior in which committed updates on cached tables in the Oracle database are automatically refreshed to the cache tables in the TimesTen database. Using a read-only cache group is suitable for reference data that is heavily accessed by applications.

See "Read-only cache group" for details about read-only cache groups.

- Asynchronous writethrough (AWT) cache group
An AWT cache group enforces a caching behavior in which committed updates on cache tables in the TimesTen database are automatically propagated to the cached tables in the Oracle database in asynchronous fashion. Using an AWT cache group is suitable for high speed data capture and online transaction processing.

See "Asynchronous writethrough (AWT) cache group" for details about AWT cache groups.

Other types of cache groups include:

- Synchronous writethrough (SWT) cache group
An SWT cache group enforces a caching behavior in which committed updates on cache tables in the TimesTen database are automatically propagated to the cached tables in the Oracle database in synchronous fashion.

See "Synchronous writethrough (SWT) cache group" for details about SWT cache groups.

- User managed cache group
A user managed cache group defines customized caching behavior.

For example, you can define a cache group that does not use automatic refresh or automatic propagation where committed updates on the cache tables are manually propagated or flushed to the cached Oracle Database tables.

You can also define a cache group that uses both automatic propagation in synchronous fashion on every table and automatic refresh.

See "User managed cache group" for details about user managed cache groups.

Transmitting updates between the TimesTen and Oracle databases

Transmitting committed updates between the TimesTen cache tables and the cached Oracle Database tables keeps these tables in the two databases synchronized.

As shown in Figure 1-4, propagate and flush are operations that transmit committed updates on cache tables in the TimesTen database to the cached tables in the Oracle database. Flush is a manual operation and propagate is an automatic operation.

Load, refresh, and autorefresh are operations that transmit committed updates on cached tables in the Oracle database to the cache tables in the TimesTen database. Load and refresh are manual operations; autorefresh is an automatic operation.

See "Flushing a user managed cache group" for information about the FLUSH CACHE GROUP statement which can only be issued on a user managed cache group.

See "Asynchronous writethrough (AWT) cache group" and "Synchronous writethrough (SWT) cache group" for details about how a propagate operation is processed on AWT and SWT cache groups, respectively.

See "Loading and refreshing a cache group" for information about the LOAD CACHE GROUP and REFRESH CACHE GROUP statements.

See "AUTOREFRESH cache group attribute" for details about an autorefresh operation.

Figure 1-4 Transmitting committed updates between the TimesTen and Oracle databases

Loading data into a cache group: Explicitly loaded and dynamic cache groups

Cache groups are categorized as either explicitly loaded or dynamic.

In an explicitly loaded cache group, cache instances are loaded manually into the TimesTen cache tables from an Oracle database by using a load or refresh operation or automatically by using an autorefresh operation. The cache tables are loaded before operations such as queries are performed on the tables. An explicitly loaded cache group is appropriate when the set of data to cache is static and can be predetermined before applications begin performing operations on the cache tables. By default, cache groups are explicitly loaded unless they are defined as dynamic.

In a dynamic cache group, cache instances are loaded into the TimesTen cache tables on demand from an Oracle database using a dynamic load operation or manually using a load operation. A manual refresh or an autorefresh operation on a dynamic cache group can result in existing cache instances being updated or deleted, but committed updates on Oracle Database data that are not being cached do not result in new cache instances being loaded into its cache tables. A dynamic cache group is appropriate when the set of data to cache is small and should not be preloaded from Oracle Database before applications begin performing operations on the cache tables.

See "Transmitting updates between the TimesTen and Oracle databases" for details about cache group load and refresh operations.

See "Loading and refreshing a cache group" for more details about the differences between performing a load and a refresh operation on an explicitly loaded cache group and performing the same operations on a dynamic cache group.

See "Dynamically loading a cache instance" for details about a dynamic load operation.

Any cache group type (read-only, AWT, SWT, user managed) can be defined as an explicitly loaded cache group. All cache group types except a user managed cache group that uses both the AUTOREFRESH cache group attribute and the PROPAGATE cache table attribute can be defined as a dynamic cache group.

See "Dynamic cache groups" for more information about dynamic cache groups.

Sharing data across a cache grid: Local and global cache groups

In addition to being explicitly loaded or dynamic, cache groups are also classified as either local or global.

In a local cache group, data in the cache tables is not shared across TimesTen databases even if the databases are members of the same cache grid. Therefore, the databases can have overlapping data because the cache instances are local to a specific grid member. Committed updates on the TimesTen cache tables are propagated to the cached Oracle Database tables without coordination with other grid members. Any cache group type can be defined as a local cache group. A local cache group can be defined either as explicitly loaded or dynamic. Using a local cache group is suitable for reference data that is read frequently and can be present in all grid members and for disjoint data that is logically partitioned for optimal concurrency and throughput. By default, cache groups are local unless they are defined as global.

In a global cache group, data in its cache tables are shared across TimesTen databases that are members of the same cache grid. Committed updates to the same data on different grid members are propagated to the Oracle database in the order in which they were issued within the grid to ensure read/write data consistency across the members of the grid.

A dynamic AWT cache group and an explicitly loaded AWT cache group can be defined as global cache groups. New cache instances are loaded into the cache tables of a global cache group on demand. Queries on a dynamic AWT global cache group can be satisfied by data from the local grid member on which the query is made, from remote grid members, or from the Oracle database. Queries on an explicitly loaded AWT cache group can be satisfied by data from the local grid member or from remote grid members. Using a global cache group is suitable for updatable data that can only be accessed by or present in one grid member at a time in order to ensure that the data is consistent among both the members of the grid and the Oracle database.

See "Global cache groups" for information about creating and using a global cache group.

Summary of cache group types

The table in Figure 1-5 summarizes the valid combinations of cache group types, categories and classifications available to the user at cache group creation time. The cache group categories determine how the data is loaded into the cache group. The cache group classifications determine whether data in the cache group can be shared across a cache grid.

You can create an explicitly loaded local cache group or a dynamic local cache group of any cache group type. You can create a global cache group for a cache group whose category and type is dynamic AWT or explicitly loaded AWT.

Figure 1-5 Summary of cache group types and categories

High availability caching solution

You can configure TimesTen Application-Tier Database Cache to achieve high availability of cache tables, and facilitate failover and recovery while maintaining connectivity to the Oracle database. A TimesTen database that is a participant in an active standby pair replication scheme can provide high availability for cache tables in a read-only or an AWT cache group.

An active standby pair provides for high availability of a TimesTen database. Multiple grid members provide for high availability of a TimesTen cache grid. Oracle Real Application Clusters (Oracle RAC) and Data Guard provides for high availability of an Oracle database.

See "Replicating cache tables" for information on configuring replication of cache tables.

See "Using TimesTen Application-Tier Database Cache in an Oracle RAC Environment" for more information on TimesTen Application-Tier Database Cache and Oracle RAC.

See "Using TimesTen Application-Tier Database Cache with Data Guard" for more information on TimesTen Application-Tier Database Cache and Data Guard.

2 Getting Started

This chapter illustrates the creation and use of cache groups by demonstrating how to create an explicitly loaded read-only local cache group and a dynamic updatable global cache group. In addition, this chapter demonstrates how to create a grid, since this example creates a global cache group. It also describes how to populate the cache tables, and how to observe the transfer of updates between the cache tables in the TimesTen database and the cached tables in the Oracle database.

- Setting up the Oracle Database and TimesTen systems

- Creating a cache grid

- Creating cache groups

- Attaching the TimesTen database to the cache grid

- Performing operations on the read-only cache group

- Performing operations on the dynamic updatable global cache group

- Cleaning up the TimesTen and Oracle Database systems

Setting up the Oracle Database and TimesTen systems

Before you can create a cache grid or a cache group, you must first install TimesTen and then configure the Oracle Database and TimesTen systems. See Oracle TimesTen In-Memory Database Installation Guide for information about installing TimesTen.

Complete the following tasks:

1. Create users in the Oracle database.

2. Create a DSN for the TimesTen database.

3. Create users in the TimesTen database.

4. Set the cache administration user name and password in the TimesTen database.

Create users in the Oracle database

Before you can use TimesTen Application-Tier Database Cache, you must create the following users on the Oracle Database:

- A user timesten owns Oracle Database tables that store information about the cache environment.

- One or more schema users own the Oracle Database tables to be cached in a TimesTen database. These may be existing users or new users.

- A cache administration user creates and maintains Oracle Database objects that store information used to manage the cache environment and enforce predefined behaviors of particular cache group types.

Start SQL*Plus on the Oracle Database system from an operating system shell or command prompt, and connect to the Oracle database instance as the sys user:

% cd TimesTen_install_dir/oraclescripts
% sqlplus sys as sysdba
Enter password: password

Use SQL*Plus to create a default tablespace to be used for storing TimesTen Application-Tier Database Cache management objects that should not be shared with other applications. While you may also store Oracle base tables that are cached in TimesTen, we strongly recommend that this tablespace be used solely by TimesTen for cache management.

Use SQL*Plus to run the SQL*Plus script TimesTen_install_dir/oraclescripts/initCacheGlobalSchema.sql to create the following elements:

- The timesten user

- The Oracle Database tables owned by the timesten user to store information about the cache environment, including a cache grid if one is configured

- The TT_CACHE_ADMIN_ROLE role that defines privileges on these Oracle Database tables

Pass the default tablespace as an argument to the initCacheGlobalSchema.sql script. In the following example, the name of the default tablespace is cachetblsp:

SQL> CREATE TABLESPACE cachetblsp DATAFILE 'datfttuser.dbf' SIZE 100M;
SQL> @initCacheGlobalSchema "cachetblsp"

Next, use SQL*Plus to create a schema user. Grant this user the minimum set of privileges required to create tables in the Oracle database to be cached in a TimesTen database. In the following example, the schema user is oratt:

SQL> CREATE USER oratt IDENTIFIED BY oracle;
SQL> GRANT CREATE SESSION, RESOURCE TO oratt;

Then use SQL*Plus to perform the following operations:

- Create a cache administration user.

- Run the SQL*Plus script TimesTen_install_dir/oraclescripts/grantCacheAdminPrivileges.sql to grant the cache administration user the minimum set of privileges required to perform cache grid and cache group operations.

Pass the cache administration user name as an argument to the grantCacheAdminPrivileges.sql script. In the following example, the cache administration user name is cacheuser and the name of its default tablespace is cachetblsp:

Note:
See the comments in the grantCacheAdminPrivileges.sql script for the required privileges by the user who executes this script and the privileges that this user grants to the cache administration user.

SQL> CREATE USER cacheuser IDENTIFIED BY oracle
2  DEFAULT TABLESPACE cachetblsp QUOTA UNLIMITED ON cachetblsp;
SQL> @grantCacheAdminPrivileges "cacheuser"
SQL> exit

The privileges that the cache administration user requires depend on the types of cache groups you create and the operations that you perform on the cache groups.

See "Create the Oracle database users" for more information about the timesten user, the schema users, and the cache administration user.

Create a DSN for the TimesTen database

SQL> SELECT value FROM nls_database_parameters WHERE parameter='NLS_CHARACTERSET';

On UNIX, in the .odbc.ini file that resides in your home directory or the TimesTen_install_dir/info/sys.odbc.ini file, create a TimesTen DSN cachealone1 and set the following connection attributes:

[cachealone1]
DataStore=/users/OracleCache/alone1
PermSize=64
OracleNetServiceName=oracledb
DatabaseCharacterSet=AL32UTF8
CacheGridEnable=1

On Windows, create a TimesTen user DSN or system DSN cachealone1 and set the following connection attributes:

- Data Store Path + Name: c:\temp\alone1

- Permanent Data Size: 64

- Oracle Net Service Name: oracledb

- Database Character Set: AL32UTF8

- Cache grid is enabled so we can create a cache grid

Use the default settings for all the other connection attributes.

See "Define a DSN for the TimesTen database" for more information about defining a DSN for a TimesTen database that caches data from an Oracle database.

See "Managing TimesTen Databases" in Oracle TimesTen In-Memory Database Operations Guide for more information about TimesTen DSNs.

Note:
The term "data store" is used interchangeably with "TimesTen database".

Create users in the TimesTen database

In addition to the Oracle Database users, you must create the following TimesTen users before you can use TimesTen Application-Tier Database Cache:

- A cache manager user performs cache grid and cache group operations. The TimesTen cache manager user must have the same name as a companion Oracle Database user that can access the cached Oracle Database tables. The companion Oracle Database user can be the cache administration user, a schema user, or some other existing user. For ease of use, making the cache administration user the companion Oracle Database user of the cache manager user is preferable. The password of the cache manager user can be different than the password of the companion Oracle Database user with the same name.

Note:
See "Create the TimesTen users" for more details on the cache manager user and its companion Oracle Database user.

The cache manager user is responsible for creating and configuring the cache grid (if one has been configured) and creating the cache groups. This user can also monitor the grid itself and various operations that are performed on the cache groups.

- One or more cache table users own the cache tables. You must create a TimesTen cache table user with the same name as an Oracle Database schema user for each schema user who owns or will own Oracle Database tables to be cached in the TimesTen database. The password of a cache table user can be different than the password of the Oracle Database schema user with the same name.
The owner and name of a TimesTen cache table is the same as the owner and name of the corresponding cached Oracle Database table.

Start the ttIsql utility on the TimesTen system from an operating system shell or command prompt as the instance administrator, and connect to the cachealone1 DSN to create the TimesTen database that is to be used to cache data from an Oracle database:

% ttIsql cachealone1

Use ttIsql to create a cache manager user. Grant this user the minimum set of privileges required to create a cache grid (if one is configured), to create cache groups, and to perform operations on the cache groups. In the following example, the cache manager user name is cacheuser, which is the same name as the cache administration user that was created earlier:

Command> CREATE USER cacheuser IDENTIFIED BY timesten;
Command> GRANT CREATE SESSION, CACHE_MANAGER, CREATE ANY TABLE TO cacheuser;

Then, use ttIsql to create a cache table user. In the following example, the cache table user name is oratt, which is the same name as the Oracle Database schema user that was created earlier:

Command> CREATE USER oratt IDENTIFIED BY timesten;
Command> exit

The privileges that the cache manager user requires depend on the types of cache groups you create and the operations that you perform on the cache groups. See "Create the TimesTen users" for more information about the cache manager user and the cache table users.

See "Managing Access Control" in Oracle TimesTen In-Memory Database Operations Guide for more information about TimesTen users and privileges.

Set the cache administration user name and password in the TimesTen database

Start the ttIsql utility and connect to the cachealone1 DSN as the cache manager user. In the connection string, specify the cache manager user name in the UID connection attribute. Specify the cache manager user's password in the PWD connection attribute. Specify the password of its companion Oracle user (created with the same name to be the companion user to the cache manager) in the OraclePWD connection attribute within the connection string. In this example, the cache administration user is the companion user to the cache manager user and so its password is provided.

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"

Use ttIsql to call the ttCacheUidPwdSet built-in procedure to set the cache administration user name and password:

Command> call ttCacheUidPwdSet('cacheuser','oracle');

The cache administration user name and password need to be set only once in a TimesTen database. See "Set the cache administration user name and password" for information on how to use this setting by the TimesTen database.

Creating a cache grid

Since this example uses a global cache group, you need to create a cache grid to define the framework used to manage global cache data within TimesTen databases that cache data from an Oracle database. You create the cache grid after you have created the Oracle Database users, the TimesTen database, and the TimesTen users, and set the cache administration user name and password in the TimesTen database.

As the cache manager user, use the ttIsql utility to call the ttGridCreate built-in procedure to create a cache grid myGrid:

Command> call ttGridCreate('myGrid');

Then use ttIsql to call the ttGridNameSet built-in procedure to associate the TimesTen database with the myGrid cache grid:

Command> call ttGridNameSet('myGrid');

See "Configuring a cache grid" for more information about the contents and functionality of a cache grid.

Creating cache groups

This section creates a read-only cache group (as shown in Figure 2-1) and an asynchronous writethrough (AWT) cache group (as shown in Figure 2-2).

Figure 2-1 Single-table read-only cache group

Figure 2-2 Single-table writethrough cache group

Complete the following tasks to create a read-only cache group and an AWT cache group:

1. Create the Oracle Database tables to be cached.

2. Start the cache agent.

3. Create the cache groups.

4. Start the replication agent for the AWT cache group.

Create the Oracle Database tables to be cached

Start SQL*Plus and connect to the Oracle database as the schema user:

% sqlplus oratt/oracle

Use SQL*Plus to create a table readtab as shown in Figure 2-3, and a table writetab as shown in Figure 2-4:

SQL> CREATE TABLE readtab (keyval NUMBER NOT NULL PRIMARY KEY, str VARCHAR2(32));
SQL> CREATE TABLE writetab (pk NUMBER NOT NULL PRIMARY KEY, attr VARCHAR2(40));

Figure 2-3 Creating an Oracle Database table to be cached in a read-only cache group

Figure 2-4 Creating an Oracle Database table to be cached in an AWT cache group

Then use SQL*Plus to insert some rows into the readtab and writetab tables, and commit the changes:

SQL> INSERT INTO readtab VALUES (1, 'Hello');
SQL> INSERT INTO readtab VALUES (2, 'World');

SQL> INSERT INTO writetab VALUES (100, 'TimesTen');
SQL> INSERT INTO writetab VALUES (101, 'CACHE');
SQL> COMMIT;

Next use SQL*Plus to grant the SELECT privilege on the readtab table, and the SELECT, INSERT, UPDATE and DELETE privileges on the writetab table to the cache administration user:

SQL> GRANT SELECT ON readtab TO cacheuser;

SQL> GRANT SELECT ON writetab TO cacheuser;
SQL> GRANT INSERT ON writetab TO cacheuser;
SQL> GRANT UPDATE ON writetab TO cacheuser;
SQL> GRANT DELETE ON writetab TO cacheuser;

The SELECT privilege on the readtab table is required to create a read-only cache group that caches this table and to perform autorefresh operations from the cached Oracle Database table to the TimesTen cache table.

The SELECT privilege on the writetab table is required to create an AWT cache group that caches this table. The INSERT, UPDATE, and DELETE privileges on the writetab table are required to perform writethrough operations from the TimesTen cache table to the cached Oracle Database table.

See "Grant privileges to the Oracle database users" for more information about the privileges required for the cache administration user to create and perform operations on a read-only cache group and an AWT cache group.

Start the cache agent

As the cache manager user, use the ttIsql utility to call the ttCacheStart built-in procedure to start the cache agent on the TimesTen database:

Command> call ttCacheStart;

See "Managing the cache agent" for more information about starting the cache agent.

Create the cache groups

As the cache manager user, use the ttIsql utility to create a read-only cache group readcache that caches the Oracle Database oratt.readtab table and a dynamic AWT global cache group writecache that caches the Oracle Database oratt.writetab table:

Command> CREATE READONLY CACHE GROUP readcache
> AUTOREFRESH INTERVAL 5 SECONDS
> FROM oratt.readtab
> (keyval NUMBER NOT NULL PRIMARY KEY, str VARCHAR2(32));

Command> CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH GLOBAL CACHE GROUP writecache
> FROM oratt.writetab
> (pk NUMBER NOT NULL PRIMARY KEY, attr VARCHAR2(40));

The cache groups readcache and writecache, and their respective cache tables oratt.readtab and oratt.writetab, whose owners and names are identical to the cached Oracle Database tables, are created in the TimesTen database. Figure 2-5 shows that the writecache cache group caches the oratt.writetab table.

Figure 2-5 Creating an asynchronous writethrough cache group

Use the ttIsql cachegroups command to view the definition of the readcache and writecache cache groups:

Command> cachegroups;

Cache Group CACHEUSER.READCACHE:

Cache Group Type: Read Only
Autorefresh: Yes
Autorefresh Mode: Incremental
Autorefresh State: Paused
Autorefresh Interval: 5 Seconds
Autorefresh Status: ok
Aging: No aging defined

Root Table: ORATT.READTAB
Table Type: Read Only

Cache Group CACHEUSER.WRITECACHE:

Cache Group Type: Asynchronous Writethrough global (Dynamic)
Autorefresh: No
Aging: LRU on

Root Table: ORATT.WRITETAB
Table Type: Propagate

2 cache groups found.

See "Read-only cache group" for more information about read-only cache groups.

See "Asynchronous writethrough (AWT) cache group" for more information about AWT cache groups.

See "Dynamic cache groups" for more information about dynamic cache groups.

See "Global cache groups" for more information about global cache groups.

Start the replication agent for the AWT cache group

As the cache manager user, use the ttIsql utility to call the ttRepStart built-in procedure to start the replication agent on the TimesTen database:

Command> call ttRepStart;

The replication agent propagates committed updates on TimesTen cache tables in AWT cache groups to the cached Oracle Database tables.

See "Managing the replication agent" for more information about starting the replication agent.

Attaching the TimesTen database to the cache grid

If you are only creating local cache groups, you do not need to attach the TimesTen database to the cache grid. However, before you can perform operations on a global cache group or on its cache tables, you must attach the TimesTen database to the cache grid that it is associated with.

As the cache manager user, use the ttIsql utility to call the ttGridAttach built-in procedure to attach the TimesTen database to the myGrid cache grid:

Command> call ttGridAttach(1,'alone1','mysys',5001);

In this example, alone1 is a name that uniquely identifies the grid member, mysys is the host name of the TimesTen system, and 5001 is the TCP/IP port for the cache agent.Calling the ttGridAttach built-in procedure automatically starts the cache agent if it is not already running.

Although the example in this chapter contains only one standalone TimesTen database as the sole grid member, it can be extended to include additional grid members such as active standby pairs and other standalone TimesTen databases. See Chapter 6, "Creating Other Cache Grid Members", for details on how to create and add other members to an existing cache grid, and how data in a global cache group is shared among the grid members.

Performing operations on the read-only cache group

This section shows how to manually load the read-only cache group. Then it shows the TimesTen cache table being automatically refreshed with committed updates on the cached Oracle Database table.

Complete the following tasks to perform operations on the read-only cache group:

1. Manually load the cache group.

2. Update the cached Oracle Database table.

Manually load the cache group

As the cache manager user, use the ttIsql utility to load the contents of the Oracle Database oratt.readtab table into the TimesTen oratt.readtab cache table in the readcache cache group:

Command> LOAD CACHE GROUP readcache COMMIT EVERY 256 ROWS;
2 cache instances affected.
Command> exit

Figure 2-6 shows that the Oracle Database data is loaded into the oratt.readtab cache table.

Figure 2-6 Loading a read-only cache group

Start the ttIsql utility and connect to the cachealone1 DSN as the instance administrator. Use ttIsql to grant the SELECT privilege on the oratt.readtab cache table to the cache manager user so that this user can issue a SELECT query on this table.

% ttIsql cachealone1
Command> GRANT SELECT ON oratt.readtab TO cacheuser;
Command> exit

Start the ttIsql utility and connect to the cachealone1 DSN as the cache manager user, including the cache manager user password and the password of its companion Oracle user. Use ttIsql to query the contents of oratt.readtab cache table.

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> SELECT * FROM oratt.readtab;
< 1, Hello >
< 2, World >
2 rows found.

See "Loading and refreshing a cache group" for more information about manually loading a cache group.

Update the cached Oracle Database table

Use SQL*Plus, as the Oracle Database schema user, to insert a new row, delete an existing row, and update an existing row in the Oracle Database readtab table, and commit the changes:

SQL> INSERT INTO readtab VALUES (3, 'Welcome');
SQL> DELETE FROM readtab WHERE keyval=2;
SQL> UPDATE readtab SET str='Hi' WHERE keyval=1;
SQL> COMMIT;

Since the read-only cache group was created specifying autorefresh with an interval of 5 seconds, the oratt.readtab cache table in the readcache cache group is automatically refreshed after 5 seconds with the committed updates on the cached Oracle Database oratt.readtab table as shown in Figure 2-7.

Figure 2-7 Automatically refresh the TimesTen cache table with Oracle Database updates

As the cache manager user, use the ttIsql utility to query the contents of the oratt.readtab cache table after the readcache cache group has been automatically refreshed with the committed updates on the cached Oracle Database table:

Command> SELECT * FROM oratt.readtab;
< 1, Hi >
< 3, Welcome >
2 rows found.
Command> exit

See "AUTOREFRESH cache group attribute" for more information about automatically refreshing cache groups.

Performing operations on the dynamic updatable global cache group

This section shows how to dynamically load the AWT cache group. Then it shows committed updates on the TimesTen cache table being automatically propagated to the cached Oracle Database table.

Complete the following tasks to perform operations on the AWT cache group:

1. Dynamically load the cache group.

2. Update the TimesTen cache table.

Dynamically load the cache group

Start the ttIsql utility and connect to the cachealone1 DSN as the instance administrator. Use ttIsql to grant the SELECT privilege on the oratt.writetab cache table to the cache manager user so that this user can issue a dynamic load SELECT statement on this table.

% ttIsql cachealone1
Command> GRANT SELECT ON oratt.writetab TO cacheuser;
Command> exit

Start the ttIsql utility and connect to the cachealone1 DSN as the cache manager user, including the cache manager user password and the password of its companion Oracle user. Use ttIsql to load a cache instance on demand from the Oracle Database oratt.writetab table to the TimesTen oratt.writetab cache table in the writecache cache group.

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> SELECT * FROM oratt.writetab WHERE pk=100;
< 100, TimesTen >
1 row found.
Command> exit

In a dynamic cache group, a cache instance can be loaded into its cache tables on demand with a dynamic load statement. A SELECT, UPDATE, DELETE or INSERT statement issued on a TimesTen cache table that uniquely identifies a cache instance results in the cache instance being automatically loaded from the cached Oracle Database table if the data is not found in the cache table. A dynamically loaded cache instance consists of a single row in the root table of the cache group, and all the related rows in the child tables.

See "Dynamically loading a cache instance" for more information about a dynamic load operation.

Data can also be manually loaded into the cache tables of a dynamic cache group using a LOAD CACHE GROUP statement.

Update the TimesTen cache table

Start the ttIsql utility and connect to the cachealone1 DSN as the instance administrator. Use ttIsql to grant the INSERT, DELETE, and UPDATE privileges on the oratt.writetab cache table to the cache manager user so that this user can perform updates on this table.

% ttIsql cachealone1
Command> GRANT INSERT ON oratt.writetab TO cacheuser;
Command> GRANT DELETE ON oratt.writetab TO cacheuser;
Command> GRANT UPDATE ON oratt.writetab TO cacheuser;
Command> exit

Start the ttIsql utility and connect to the cachealone1 DSN as the cache manager user. Use ttIsql to insert a new row, delete an existing row, and update an existing row in the oratt.writetab cache table, and commit the changes.

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> INSERT INTO oratt.writetab VALUES (102, 'Cache');
Command> DELETE FROM oratt.writetab WHERE pk=101;
Command> UPDATE oratt.writetab SET attr='Oracle' WHERE pk=100;
Command> COMMIT;
Command> exit

The committed updates on the oratt.writetab cache table in the writecache cache group are automatically propagated to the Oracle Database oratt.writetab table as shown in Figure 2-8.

Figure 2-8 Automatically propagate TimesTen cache table updates to Oracle Database

As the Oracle Database schema user, use SQL*Plus to query the contents of the writetab table:

SQL> SELECT * FROM writetab;

PK ATTR
---------- -------------------------------
100 Oracle
102 Cache

SQL> exit

Cleaning up the TimesTen and Oracle Database systems

Complete the following tasks to restore the TimesTen and Oracle Database systems to their original state before creating a cache grid and cache groups:

1. Detach the TimesTen database from the cache grid.

2. Stop the replication agent.

3. Drop the cache groups.

4. Destroy the cache grid.

5. Stop the cache agent and destroy the TimesTen database.

6. Drop the Oracle Database users and their objects.

Detach the TimesTen database from the cache grid

Start the ttIsql utility and connect to the cachealone1 DSN as the cache manager user. Since we attached to a grid, use ttIsql to call the ttGridDetach built-in procedure to detach the TimesTen database from the myGrid cache grid.

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> call ttGridDetach;

See "Detaching a TimesTen database from a cache grid" for information about the effects of detaching a TimesTen database from a cache grid.

Stop the replication agent

As the cache manager user, use the ttIsql utility to call the ttRepStop built-in procedure to stop the replication agent on the TimesTen database:

Command> call ttRepStop;
Command> exit

See "Managing the replication agent" for more information about stopping the replication agent.

Drop the cache groups

Start the ttIsql utility and connect to the cachealone1 DSN as the instance administrator. Use ttIsql to grant the DROP ANY TABLE privilege to the cache manager user so that this user can drop the underlying cache tables when dropping the cache groups.

% ttIsql cachealone1
Command> GRANT DROP ANY TABLE TO cacheuser;
Command> exit

Start the ttIsql utility and connect to the cachealone1 DSN as the cache manager user. Use ttIsql to drop the readcache read-only cache group and the writecache AWT cache group.

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> DROP CACHE GROUP readcache;
Command> DROP CACHE GROUP writecache;

The cache groups readcache and writecache, and their respective cache tables oratt.readtab and oratt.writetab, are dropped from the TimesTen database.

See "Dropping a cache group" for more information about dropping cache groups.

Destroy the cache grid

As the cache manager user, use the ttIsql utility to call the ttGridDestroy built-in procedure to destroy the myGrid cache grid:

Command> call ttGridDestroy('myGrid');

See "Destroying a cache grid" for more information about destroying a cache grid.

Stop the cache agent and destroy the TimesTen database

As the cache manager user, use the ttIsql utility to call the ttCacheStop built-in procedure to stop the cache agent on the TimesTen database:

Command> call ttCacheStop;
Command> exit

See "Managing the cache agent" for more information about stopping the cache agent.

Then use the ttDestroy utility to connect to the cachealone1 DSN and destroy the TimesTen database:

% ttDestroy cachealone1

Drop the Oracle Database users and their objects

Start SQL*Plus and connect to the Oracle database as the sys user. Use SQL*Plus to drop the timesten user, the schema user oratt, and the cache administration user cacheuser.

% sqlplus sys as sysdba
Enter password: password
SQL> DROP USER timesten CASCADE;
SQL> DROP USER oratt CASCADE;
SQL> DROP USER cacheuser CASCADE;

Specifying CASCADE in a DROP USER statement drops all objects such as tables and triggers owned by the user before dropping the user itself.

Next use SQL*Plus to drop the TT_CACHE_ADMIN_ROLE role:

SQL> DROP ROLE TT_CACHE_ADMIN_ROLE;

Then use SQL*Plus to drop the default tablespace cachetblsp used by the timesten user and cache administration user including the contents of the tablespace and its data file:

SQL> DROP TABLESPACE cachetblsp INCLUDING CONTENTS AND DATAFILES;
SQL> exit

3 Setting Up a Caching Infrastructure

The following sections describe the tasks for setting up the TimesTen and Oracle Database systems before you can start caching Oracle Database data in a TimesTen database:

- Configuring your system to cache Oracle Database data in TimesTen

- Configuring the Oracle database to cache data in TimesTen

- Configuring a TimesTen database to cache Oracle Database data

- Configuring data management

- Testing the connectivity between the TimesTen and Oracle databases

- Managing the cache agent

Configuring your system to cache Oracle Database data in TimesTen

TimesTen Application-Tier Database Cache supports the following Oracle Database Server releases:

- Oracle 11g Release 2 (11.2.0.2.0 or above)

- Oracle 11g Release 1 (11.1.0.7.0 or above)

- Oracle 10g Release 2 (10.2.0.5.0 or above)

Configure the environment variables for your particular operating system, as described in "TimesTen Application-Tier Database Cache environment variables for UNIX" or "TimesTen Application-Tier Database Cache environment variables for Microsoft Windows".

Then, install TimesTen as described in Oracle TimesTen In-Memory Database Installation Guide.

Note:
From a product perspective, "TimesTen Application-Tier Database Cache" is used interchangeably with "TimesTen" because the TimesTen Application-Tier Database Cache product option includes the Oracle TimesTen In-Memory Database.

TimesTen does not support Oracle Name Server for Windows clients.

TimesTen Application-Tier Database Cache environment variables for UNIX

The shared library search path environment variable such as LD_LIBRARY_PATH or SHLIB_PATH must include the TimesTen_install_dir/lib directory.

For more information, see "Shared library path environment variable" in Oracle TimesTen In-Memory Database Installation Guide.

The PATH environment variable must include the TimesTen_install_dir/bin directory.

In the following example, TimesTen is installed in the /timesten/myinstance directory:

LD_LIBRARY_PATH=/timesten/myinstance/lib
PATH=/timesten/myinstance/bin

TimesTen Application-Tier Database Cache environment variables for Microsoft Windows

The PATH system environment variable must include the following directories:

- Oracle_install_dir\bin

- TimesTen_install_dir\lib

- TimesTen_install_dir\bin

In the following example, Oracle Database is installed in the C:\oracle\ora112 directory and TimesTen is installed in the C:\timesten\myinstance directory:

PATH=C:\oracle\ora112\bin;C:\timesten\myinstance\lib;C:\timesten\myinstance\bin

Configuring the Oracle database to cache data in TimesTen

The following sections describe the tasks that must be performed on the Oracle database by the sys user:

- Create the Oracle database users

- Grant privileges to the Oracle database users

- Automatically create Oracle Database objects used to manage data caching

- Manually create Oracle Database objects used to manage data caching

Create the Oracle database users

You must create a default tablespace and a user timesten that is to own the Oracle Database tables that store information about cache operations.

Create or designate a default tablespace for the timesten user, which is passed as an argument to the initCacheGlobalSchema.sql script. This tablespace is used for storing TimesTen Application-Tier Database Cache management objects that should not be shared with other applications. While you may also store Oracle base tables that are cached in TimesTen, we strongly recommend that this tablespace be used solely by TimesTen for cache management.

Execute the SQL*Plus script TimesTen_install_dir/oraclescripts/initCacheGlobalSchema.sql, which creates:

- The timesten user

- The Oracle Database tables owned by the timesten user to store information about the cache environment, including a cache grid if one is configured

- The TT_CACHE_ADMIN_ROLE role that defines privileges on these Oracle Database tables

See "Managing a caching environment with Oracle Database objects" for a list of Oracle Database tables owned by the timesten user.

Example 3-1 Creating the timesten user and its tables

In the following SQL*Plus example, the default tablespace that is created for the timesten user is cachetblsp.

% cd TimesTen_install_dir/oraclescripts
% sqlplus sys as sysdba
Enter password: password
SQL> CREATE TABLESPACE cachetblsp DATAFILE 'datfttuser.dbf' SIZE 100M;
SQL> @initCacheGlobalSchema "cachetblsp"

Create or designate one or more users to own Oracle Database tables that are to be cached in a TimesTen database. These users are the schema users. These may be existing users or new users. The tables to be cached may or may not already exist.

Example 3-2 Creating a schema user

As the sys user, the following SQL*Plus example creates a schema user oratt.

SQL> CREATE USER oratt IDENTIFIED BY oracle;

Next, you must create a user that creates, owns, and maintains Oracle Database objects that store information used to manage the cache environment (including a cache grid if one is configured) for a TimesTen database and enforce predefined behaviors of particular cache group types. We refer to this user as the cache administration user.

Note:
Each TimesTen database can be managed by only a single cache administration user on the Oracle database. However, a single cache administration user can manage multiple TimesTen databases. You can specify one or more cache administration users where each manages one or more TimesTen databases.
For more details, see "Caching the same Oracle table on two or more TimesTen databases".

Designate the tablespace that was created for the timesten user as the default tablespace for the cache administration user. This user creates tables in this tablespace that are used to store information about the cache environment and its cache groups. Other Oracle Database objects (such change log tables, replication metadata tables, and triggers) are used to enforce the predefined behaviors of autorefresh cache groups and AWT cache groups are created in the same tablespace. To create and manage these objects, the cache administration user must have a high level of privileges.

Note:
If you create multiple cache administration users, each may use the same or different tablespace as their default tablespace.

See "Managing a caching environment with Oracle Database objects" for a list of Oracle Database tables and triggers owned by the cache administration user.

Note:
An autorefresh cache group refers to a read-only cache group or a user managed cache group that uses the AUTOREFRESH MODE INCREMENTAL cache group attribute.

Example 3-3 Creating the cache administration user

As the sys user, create a cache administration user cacheuser. In the following example, the default tablespace for the cacheuser user is cachetblsp.

Use SQL*Plus to create the cache administration user:

SQL> CREATE USER cacheuser IDENTIFIED BY oracle
2  DEFAULT TABLESPACE cachetblsp QUOTA UNLIMITED ON cachetblsp;

Grant privileges to the Oracle database users

The cache administration user must be granted a high level of privileges depending on the cache group types created and the operations performed on these cache groups. You can run the SQL*Plus script TimesTen_install_dir/oraclescripts/grantCacheAdminPrivileges.sql as the sys user to grant the cache administration user the minimum set of privileges required to perform cache grid and cache group operations. For more information on this SQL script, see "Automatically create Oracle Database objects used to manage data caching".

The entire list of privileges required for this user for each cache operation are listed in the first column of Table A-1 that is detailed in "Required privileges for the cache administration user and the cache manager user".

Automatically create Oracle Database objects used to manage data caching

TimesTen can automatically create Oracle Database objects owned by the cache administration user, such as cache and replication metadata tables, change log tables, and triggers when particular cache environment, cache group, and cache grid operations are performed. Some of these objects are used to store information about TimesTen databases that are associated with a particular cache grid. Other objects are used to enforce the predefined behaviors of autorefresh cache groups and AWT cache groups.

These Oracle Database objects are automatically created if the cache administration user has been granted the required privileges by running the SQL*Plus script TimesTen_install_dir/oraclescripts/grantCacheAdminPrivileges.sql as the sys user. The set of required privileges include CREATE SESSION, RESOURCE, CREATE ANY TRIGGER, and the TT_CACHE_ADMIN_ROLE role. The cache administration user name is passed as an argument to the grantCacheAdminPrivileges.sql script.

Note:
Alternatively, you can manually create these objects as described in "Manually create Oracle Database objects used to manage data caching" before performing any cache grid or cache group operations if, for security purposes, you do not want to grant the RESOURCE or CREATE ANY TRIGGER privileges to the cache administration user required to automatically create these tables and triggers.

In addition to the privileges granted to the cache administration user by running the grantCacheAdminPrivileges.sql script, this user may also need to be granted privileges such as SELECT or INSERT on the cached Oracle Database tables depending on the types of cache groups you create, and the operations that you perform on the cache groups and their cache tables. See Table A-1 for a complete list of privileges that need to be granted to the cache administration user in order to perform particular cache grid, cache group, and cache table operations.

Example 3-4 Granting privileges to automatically create Oracle Database objects

As the sys user, run the grantCacheAdminPrivileges.sql script to grant privileges to the cache administration user to automatically create Oracle Database objects used to manage caching Oracle Database data in a TimesTen database. In the following example, the cache administration user name is cacheuser.

Use SQL*Plus to run the grantCacheAdminPrivileges.sql script:

SQL> @grantCacheAdminPrivileges "cacheuser"
SQL> exit

For example, with autorefresh cache groups, the Oracle Database objects used to enforce the predefined behaviors of these cache group types are automatically created if the objects do not already exist and one of the following occurs:

- The cache group is created with its autorefresh state set to PAUSED or ON.

- The cache group is created with its autorefresh state set to OFF and then altered to either PAUSED or ON.

Manually create Oracle Database objects used to manage data caching

The cache administration user requires the RESOURCE privilege to automatically create the Oracle Database objects used to:

- Store information about TimesTen databases that are associated with a particular cache environment, including a cache grid if one is configured.

- Enforce the predefined behaviors of autorefresh cache groups. In this case, the cache administration user also requires the CREATE ANY TRIGGER privilege to automatically create these Oracle Database objects.

- Enforce the predefined behaviors of AWT cache groups.

For security purposes, if you do not want to grant the RESOURCE and CREATE ANY TRIGGER privileges to the cache administration user required to automatically create the Oracle Database objects, you can manually create these objects.

To manually create the Oracle Database tables and triggers used to enforce the predefined behaviors of particular cache group types, run the SQL*Plus script TimesTen_install_dir/oraclescripts/initCacheAdminSchema.sql as the sys user. These objects must be created before you can create autorefresh cache groups and AWT cache groups. The cache administration user name is passed as an argument to the initCacheAdminSchema.sql script.

The initCacheAdminSchema.sql script also grants a minimal set of required privileges including CREATE SESSION and the TT_CACHE_ADMIN_ROLE role to the cache administration user. In addition to the privileges granted to the cache administration user by running the initCacheAdminSchema.sql script, this user may also need to be granted privileges such as SELECT or INSERT on the cached Oracle Database tables depending on the types of cache groups you create and the operations that you perform on the cache groups and their cache tables. See Table A-1 for a complete list of privileges that need to be granted to the cache administration user in order to perform particular cache grid, cache group, and cache table operations.

To manually create the Oracle Database tables used to store information about TimesTen databases that are associated with a particular cache grid, run the SQL*Plus script TimesTen_install_dir/oraclescripts/initCacheGridSchema.sql as the sys user. These tables must be created before you can create a cache grid. The cache administration user name and the name of the cache grid that you create are passed as arguments to the initCacheGridSchema.sql script.

Example 3-5 Manually creating Oracle Database objects used to manage caching data

As the sys user, run the initCacheAdminSchema.sql script to manually create Oracle Database objects used to enforce the predefined behaviors of autorefresh cache groups and AWT cache groups, and grant a limited set of privileges to the cache administration user. Then, run the initCacheGridSchema.sql script to manually create Oracle Database objects used to store information about TimesTen databases associated with a particular cache grid. In the following example, the cache administration user name is cacheuser and the cache grid name is ttGrid.

Use SQL*Plus to run the initCacheAdminSchema.sql and initCacheGridSchema.sql scripts:

SQL> @initCacheAdminSchema "cacheuser"
SQL> @initCacheGridSchema "cacheuser" "ttGrid"
SQL> exit

Other Oracle Database objects associated with Oracle Database tables that are cached in an autorefresh cache group are needed to enforce the predefined behaviors of these cache group types. See "Manually creating Oracle Database objects for autorefresh cache groups" for details about how to create these additional objects after you create the cache group.

To view a list of the Oracle Database objects created and used by TimesTen to manage the caching of Oracle Database data, execute the following query in SQL*Plus as the sys user:

SQL> SELECT owner, object_name, object_type FROM all_objects WHERE object_name
2  LIKE 'TT\___%' ESCAPE '\';

The query returns a list of tables, indexes, and triggers owned by either the timesten user or the cache administration user.

Configuring a TimesTen database to cache Oracle Database data

The following sections describe the operations that must be performed on the TimesTen database by the instance administrator or the cache manager user:

- Define a DSN for the TimesTen database

- Create the TimesTen users

- Grant privileges to the TimesTen users

- Set the cache administration user name and password

Define a DSN for the TimesTen database

A TimesTen database that caches data from an Oracle database can be referenced by either a system DSN or a user DSN. See "Managing TimesTen Databases" in Oracle TimesTen In-Memory Database Operations Guide for more information about creating TimesTen DSNs.

When creating a DSN for a TimesTen database that caches data from an Oracle database, pay special attention to the settings of the following connection attributes. All of these connection attributes can be set in a Data Manager DSN or a connection string, unless otherwise stated.

- PermSize specifies the allocated size of the database's permanent region in MB. Set this value to at least 32 MB.

- OracleNetServiceName must be set to the net service name of the Oracle database instance.
On Microsoft Windows systems, the net service name of the Oracle database instance is specified in the Oracle Net Service Name field of the TimesTen Cache tab within the TimesTen ODBC Setup dialog box.

- DatabaseCharacterSet must be set to the Oracle database character set.
You can determine the Oracle database character set by executing the following query in SQL*Plus as any user:

SQL> SELECT value FROM nls_database_parameters
2 WHERE parameter='NLS_CHARACTERSET';

- UID specifies the name of a cache user, such as the cache manager user, that has the same name as a companion Oracle Database user who can access the cached Oracle Database tables. The UID connection attribute can be specified in a Data Manager DSN, a client DSN, or a connection string.

- PWD specifies the password of the TimesTen user specified in the UID connection attribute. The PWD connection attribute can be specified in a Data Manager DSN, a client DSN, or a connection string.

- OraclePWD specifies the password of the companion Oracle Database user that has the same name as the TimesTen user specified in the UID connection attribute and can access the cached Oracle Database tables.

Note:
See "Create the TimesTen users" for more details on the cache manager user and its companion Oracle Database user.

- PassThrough can be set to control whether statements are to be executed in the TimesTen database or passed through to be executed in the Oracle database. See "Setting a passthrough level".

- LockLevel must be set to its default of 0 (row-level locking) because TimesTen Application-Tier Database Cache does not support database-level locking.

- TypeMode must be set to its default of 0 (Oracle Database type mode).

- ReplicationApplyOrdering and CacheAWTParallelism control parallel propagation of changes to TimesTen cache tables in an AWT cache group to the corresponding Oracle Database tables. See "Configuring parallel propagation to Oracle Database tables".

- CacheGridEnable configures whether you will create a cache grid to manage global cache groups. Set to 0 if you are not planning on using a cache grid; set to 1 if you are planning on using a cache grid.

Example 3-6 DSN for a TimesTen database that caches data from an Oracle database

The following example is the definition of the cachealone1 DSN that references the first standalone TimesTen database that becomes a member of the ttGrid cache grid:

[cachealone1]
DataStore=/users/OracleCache/alone1
PermSize=64
OracleNetServiceName=orcl
DatabaseCharacterSet=WE8ISO8859P1
CacheGridEnable=1

Create the TimesTen users

First, you must create a user who performs cache grid (if one is configured) and cache group operations. We refer to this user as the cache manager user. The TimesTen cache manager user must have the same name as a companion Oracle Database user that can access the cached Oracle Database tables. For example, the companion Oracle Database user must have privileges to select from and update the cached Oracle Database tables. The companion Oracle Database user can be the cache administration user, a schema user, or some other existing user. For ease of use, making the cache administration user be the companion Oracle Database user of the cache manager user is preferable; however, if you are concerned with the high level of privileges assigned to the cache administration user, then choose another Oracle Database user as the companion Oracle user. The password of the cache manager user can be different than the password of the companion Oracle Database user with the same name.

Note:
You can create multiple cache manager users on a TimesTen database, such as one for each TimesTen DBA. However, you can only define a single cache administration user on the Oracle database for this particular TimesTen database. (You can use the same cache administration user for all TimesTen databases that connect to the Oracle database or define a separate cache administration user for each TimesTen database.) If you create multiple cache manager users, one or more of these users can use the cache administration user as its companion Oracle user.

The cache manager user creates and configures the cache grid, if one is configured, and creates the cache groups. It may perform operations such as loading or refreshing a cache group although these operations can be performed by any TimesTen user that has sufficient privileges. The cache manager user can also monitor various aspects of the caching environment, such as the grid itself or asynchronous operations that are performed on cache groups such as autorefresh.

Then, you must create a user with the same name as an Oracle Database schema user for each schema user who owns or will own Oracle Database tables to be cached in the TimesTen database. We refer to these users as cache table users, because the TimesTen cache tables are to be owned by these users. Therefore, the owner and name of a TimesTen cache table is the same as the owner and name of the corresponding cached Oracle Database table. The password of a cache table user can be different than the password of the Oracle Database schema user with the same name.

Operations on a cache group or a cache table, such as loading a cache group or updating a cache table, can be performed by any TimesTen user that has sufficient privileges. In the examples throughout this guide, the cache manager user performs these types of operations although these operations can be performed by another user, such as a cache table user, that has the required privileges. If these operations are to be performed by a TimesTen user other than the cache manager user, the other user must have the same name as a companion Oracle Database user that can select from and update the cached Oracle Database tables. Connect to the TimesTen database specifying that user's name in the UID connection attribute, and supply the corresponding TimesTen and Oracle Database passwords in the PWD and OraclePWD connection attributes, respectively, to perform operations on a cache group or cache table.

Example 3-7 Creating the TimesTen users

In the following ttIsql utility example, create the TimesTen database by connecting to the cachealone1 DSN as the instance administrator. Then create the cache manager user cacheuser whose name, in this example, is the same as the cache administration user, who will also act as the cache manager's companion Oracle user. Then, create a cache table user oratt whose name is the same as the Oracle Database schema user who is to own the Oracle Database tables to be cached in the TimesTen database.

% ttIsql cachealone1
Command> CREATE USER cacheuser IDENTIFIED BY timesten;
Command> CREATE USER oratt IDENTIFIED BY timesten;

Grant privileges to the TimesTen users

The privileges that the TimesTen users require depend on the types of cache groups you create and the operations that you perform on the cache groups. All of the privileges required for the TimesTen cache manager user for each cache operation are listed in the second column in Table A-1.

Example 3-8 Granting privileges to the cache manager user

The cacheuser cache manager user requires privileges to perform the following operations:

- Set the cache administration user and password (CACHE_MANAGER).

- Create and associate the TimesTen database with a cache grid (CACHE_MANAGER).

- Start the cache agent and replication agent processes on the TimesTen database (CACHE_MANAGER).

- Attach the TimesTen database to the cache grid (CACHE_MANAGER).

- Create cache groups to be owned by the cache manager user (CREATE CACHE GROUP, inherited by the CACHE_MANAGER privilege; CREATE ANY TABLE to create the underlying cache tables which are to be owned by the oratt cache table user).

As the instance administrator, use the ttIsql utility to grant the cacheuser cache manager user the required privileges:

Command> GRANT CREATE SESSION, CACHE_MANAGER, CREATE ANY TABLE TO cacheuser;
Command> exit

Set the cache administration user name and password

You must set the cache administration user name and password in the TimesTen database before any cache grid or cache group operation can be issued with the ttCacheUidPwdSet built-in procedure. The cache agent connects to the Oracle database as this user to create and maintain Oracle Database objects that store information used to manage a cache grid and enforce predefined behaviors of particular cache group types. In addition, both the cache and replication agents connect to the Oracle database with the credentials set with the ttCacheUidPwdSet built-in procedure to manage Oracle database operations.

Note:
When you connect to the TimesTen database to work with AWT or read-only cache groups, TimesTen uses the credentials set with the ttCacheUidPwdSet built-in procedure when connecting to the Oracle database on behalf of these cache groups.
When you connect to the TimesTen database to work with SWT or user managed cache groups or passthrough operations, TimesTen connects to the Oracle database using the current user's credentials as the user name and the OraclePwd connection attribute as the Oracle password. Thus, the correct user name and Oracle database password that should be used for connecting to the Oracle database must be set correctly in the connection string or with the connection attributes.

The cache administration user name and password need to be set only once in each TimesTen database that caches Oracle Database data unless it needs to be changed. For example, if you modify the password of the cache administration user, if the TimesTen database is destroyed and re-created, or if the cache administration user name is dropped and re-created in the Oracle database, the cache administration user name and password must be set again.

The cache administration user name cannot be changed if there are cache groups in the database. The cache groups must be dropped before you can drop and recreate the cache administration user. See "Changing cache user names and passwords" for more details.

Example 3-9 Setting the cache administration user name and password

The cache administration user name and password can be set programmatically by calling the ttCacheUidPwdSet built-in procedure after connecting as the cache manager user:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> call ttCacheUidPwdSet('cacheuser','oracle');

It can also be set from a command line by running a ttAdmin -cacheUidPwdSet utility command as a TimesTen external user with the CACHE_MANAGER privilege:

% ttAdmin -cacheUidPwdSet -cacheUid cacheuser -cachePwd oracle cachealone1

If you do not specify the -cachePwd option, the ttAdmin utility prompts for the cache administration user's password.

For more information about the utility, see "ttAdmin" in Oracle TimesTen In-Memory Database Reference.

Configuring data management

You can configure how TimesTen manages cached data either locally in a single TimesTen database or globally across multiple TimesTen in-memory databases.

- Manage data locally, where each TimesTen in-memory database operates separately from other TimesTen in-memory databases. While this option is simpler, TimesTen does not manage data coherence across all TimesTen in-memory databases. For more details, see "Managing data locally".

- Manage data globally across multiple TimesTen in-memory databases with a cache grid. This is the default method. A cache grid is a collection of TimesTen Cache databases that collectively manage application data located within global cache groups. A cache grid contains a set of distributed TimesTen in-memory databases that work together to cache data from an Oracle database and guarantee cache coherence for global cache groups located on these TimesTen databases. See "Configuring a cache grid" for more information.

Managing data locally

If you are not planning to use global cache groups, you do not need to create a cache grid. In this case, set the CacheGridEnable connection attribute to 0, which can be configured in the DSN as described in "Define a DSN for the TimesTen database".

This connection attribute states that you will not use global cache groups. Once set, TimesTen does not require you to create a cache grid or associate the TimesTen database with the grid before cache groups can be created within that database.

Note:
While you may have multiple TimesTen in-memory databases that interact with the same Oracle database, they will each operate independently. Thus, any data cached in separate TimesTen databases will each interact with the Oracle database independently.
Use a cache grid if you want to scale data across several TimesTen databases with read and write data consistency and predictable latency for their database transactions.

With this option, you cannot create global cache groups within that database. If, at some point in the future, you decide to use global cache groups within a cache grid, perform the following:

1. Drop all existing cache groups.

2. Create the cache grid and associate the TimesTen in-memory database as a member, as described in "Overview of a cache grid".

3. Recreate all pre-existing cache groups.

See "Global cache groups" for more information about global cache groups.

Configuring a cache grid

An Oracle Database table cannot be cached in separate cache groups within the same TimesTen database. However, the table can be cached in separate cache groups within different TimesTen databases.

A TimesTen cache grid provides users with Oracle databases a means to horizontally scale out cache groups across multiple systems with read and write data consistency across the TimesTen databases and predictable latency for database transactions. A cache grid contains one or more grid members that collectively manage application data using the relational data model. A grid member is either a standalone TimesTen database or an active standby pair that consists of at least two replicated TimesTen databases.

Each database of a grid member is called a grid node. A node is a single TimesTen database that is either a standalone database, or the active database or standby database of an active standby pair. Therefore, a grid member is composed of one or two nodes.

Note:
See "Administering an Active Standby Pair with Cache Groups" in Oracle TimesTen In-Memory Database Replication Guide for more information about replicating cache tables.

Grid members can reside on the same system or on different systems. If the grid members reside across different systems, the systems must be connected to each other in a TCP/IP private network. Each system must have the same machine architecture, operating system version, platform, and bit version. The TimesTen major release number of all grid members must be the same.

A TimesTen database that is or is part of a grid member can contain local and global cache groups as well as explicitly loaded and dynamic cache groups.

Note:
See "Dynamic cache groups" for more information about dynamic cache groups.
See "Global cache groups" for more information about global cache groups.

A cache grid can be associated with only one Oracle database. A TimesTen database can be a member of only one cache grid. An Oracle database can be associated with more than one cache grid and each grid can be administered by a different cache administration user. A cache grid has no association with other cache grids.

The following sections describe the operations that must be performed on the TimesTen database by the cache manager user:

- Modify the PROCESSES system parameter for ten or more grid nodes

- Create a cache grid

- Associate a TimesTen database with a cache grid

Modify the PROCESSES system parameter for ten or more grid nodes

If you are planning a grid with ten or more nodes, modify the PROCESSES Oracle Database system parameter. Use this guideline:

PROCESSES >= 10*GridMembers + DLConnections + OraBackgroundProcesses

where:

- GridMembers = number of grid members

- DLConnections = number of dynamic load connections

- OraBackgroundProcesses = number of Oracle Database background processes

The number of dynamic load connections is determined by how many sessions are to have dynamic cache group operations.

For more information about modifying an Oracle Database system parameter, see "Changing Parameter Values in a Parameter File" in Oracle Database Reference. For more information about Oracle Database background processes, see "Background Processes" in Oracle Database Reference.

Create a cache grid

The examples in the rest of this guide create a cache grid ttGrid that contains three grid members: two standalone TimesTen databases and an active standby pair consisting of three TimesTen databases. This chapter shows how to associate one of the standalone databases with the cache grid. Subsequent chapters show how to create the other standalone database and the active standby pair, and how to associate those members with the grid.

See Example 3-6 for the DSN definition of the first standalone TimesTen database.

You can create a cache grid from any of the standalone databases, or from either the active or standby database of the active standby pair. A cache grid is created only once from any one of the grid members.

Example 3-10 Creating a cache grid

Create the ttGrid cache grid from the first standalone database by calling the ttGridCreate built-in procedure as the cache manager user:

Command> call ttGridCreate('ttGrid');

All the databases in these examples, except for the read-only subscriber database of the active standby pair, are associated with the ttGrid cache grid.

If you manually created the Oracle Database objects used to store information about TimesTen databases that are associated with a particular cache grid as described in "Manually create Oracle Database objects used to manage data caching", you do not need to call ttGridCreate because the grid, in effect, was created by running the initCacheGridSchema.sql script.

You can associate a TimesTen database with a cache grid before creating cache groups in the database. If you do not want to use a cache grid, you can set the CacheGridEnable connection attribute to 0 so that you do not have to create a cache grid and associate the TimesTen database with the grid before cache groups can be created within that database.

See "Global cache groups" for more information about global cache groups.

CacheGridEnable is set to 1 by default.

Associate a TimesTen database with a cache grid

All standalone databases, and the active and standby databases of the active standby pair must be associated with a cache grid before you can create cache groups within those databases.

Example 3-11 Associating a TimesTen database with a cache grid

Associate the first standalone database to the ttGrid cache grid by calling the ttGridNameSet built-in procedure as the cache manager user:

Command> call ttGridNameSet('ttGrid');

Testing the connectivity between the TimesTen and Oracle databases

To test the connectivity between the TimesTen and Oracle databases, set the passthrough level to 3 and execute the following query, to be processed on the Oracle database, as the cache manager user:

Command> passthrough 3;
Command> SELECT * FROM V$VERSION;
Command> passthrough 0;

If connectivity has been successfully established, the query returns the version of the Oracle database. If it does not, check the following for correctness:

- The Oracle Net service name set in the OracleNetServiceName connection attribute and the state of the Oracle database server

- The settings of the shared library search path environment variable such as LD_LIBRARY_PATH or SHLIB_PATH

- The setting of the cache administration user name in the TimesTen database

Example 3-12 Determining the cache administration user name setting

The cache administration user name setting can be returned programmatically by calling the ttCacheUidGet built-in procedure as the cache manager user:

Command> call ttCacheUidGet;

It can also be returned from a command line by running a ttAdmin -cacheUidGet utility command as a TimesTen external user with the CACHE_MANAGER privilege:

% ttAdmin -cacheUidGet cachealone1

Managing the cache agent

The cache agent is a TimesTen process that performs cache operations such as loading a cache group and autorefresh, as well as manages Oracle Database objects used to enforce the predefined behaviors of particular cache group types.

Example 3-13 Starting the cache agent

The cache agent can be manually started programmatically by calling the ttCacheStart built-in procedure as the cache manager user:

Command> call ttCacheStart;

It can also be started from a command line by running a ttAdmin -cacheStart utility command as a TimesTen external user with the CACHE_MANAGER privilege:

% ttAdmin -cacheStart cachealone1

Example 3-14 Stopping the cache agent

The cache agent can be manually stopped programmatically by calling the ttCacheStop built-in procedure as the cache manager user:

Command> call ttCacheStop;

It can also be stopped from a command line by running a ttAdmin -cacheStop utility command as a TimesTen external user with the CACHE_MANAGER privilege:

% ttAdmin -cacheStop cachealone1

The ttCacheStop built-in procedure has an optional parameter and the ttAdmin -cacheStop utility command has an option -stopTimeout that specifies how long the TimesTen main daemon process waits for the cache agent to stop. If the cache agent does not stop within the specified timeout period, the TimesTen daemon stops the cache agent. The default cache agent stop timeout is 100 seconds. A value of 0 specifies to wait indefinitely.

Do not stop the cache agent immediately after you have dropped or altered an autorefresh cache group. Instead, wait for at least two minutes to allow the cache agent to clean up Oracle Database objects such as change log tables and triggers that were created and used to manage the cache group.

Note:
The TimesTen X/Open XA and Java Transaction API (JTA) implementations do not work with TimesTen Application-Tier Database Cache. The start of any XA or JTA transaction fails if the cache agent is running.

Set a cache agent start policy

A cache agent start policy determines how and when the cache agent process starts on a TimesTen database. The cache agent start policy can be set to:

- manual

- always

- norestart

The default start policy is manual, which means the cache agent must be started manually by calling the ttCacheStart built-in procedure or running a ttAdmin -cacheStart utility command. To manually stop a running cache agent process, call the ttCacheStop built-in procedure or run a ttAdmin -cacheStop utility command.

When the start policy is set to always, the cache agent starts automatically when the TimesTen main daemon process starts. With the always start policy, the cache agent cannot be stopped when the main daemon is running unless the start policy is first changed to either manual or norestart. Then issue a manual stop by calling the ttCacheStop built-in procedure or running a ttAdmin -cacheStop utility command.

With the manual and always start policies, the cache agent automatically restarts when the database recovers after a failure such as a database invalidation. If the database was attached to a cache grid when the failure occurred, it is automatically reattached to the grid when the database recovers.

Setting the cache agent start policy to norestart means the cache agent must be started manually by calling the ttCacheStart built-in procedure or running a ttAdmin -cacheStart utility command, and stopped manually by calling the ttCacheStop built-in procedure or running a ttAdmin -cacheStop utility command.

With the norestart start policy, the cache agent does not automatically restart when the database recovers after a failure such as a database invalidation. You must restart the cache agent manually by calling the ttCacheStart built-in procedure or running a ttAdmin -cacheStart utility command. If the database was attached to a cache grid when the failure occurred, it is not automatically reattached to the grid when the database recovers. You must call the ttGridAttach built-in procedure to reattach the database to the grid.

Note:
For more details, see "ttAdmin," "ttCachePolicySet," "ttCacheStart," "ttCacheStop," and "ttGridAttach" in the Oracle TimesTen In-Memory Database Reference.

Example 3-15 Setting a cache agent start policy

The cache agent start policy can be set programmatically by calling the ttCachePolicySet built-in procedure as the cache manager user:

Command> call ttCachePolicySet('always');

It can also be set from a command line by running a ttAdmin -cachePolicy utility command as a TimesTen external user with the CACHE_MANAGER privilege:

% ttAdmin -cachePolicy norestart cachealone1

4 Defining Cache Groups

The following sections describe the different types of cache groups and how to define them:

- Cache groups and cache tables

- Creating a cache group

- Caching Oracle Database synonyms

- Caching Oracle Database LOB data

- Implementing aging in a cache group

- Dynamic cache groups

- Global cache groups

Cache groups and cache tables

A cache group defines the Oracle Database data to cache in the TimesTen database. When you create a cache group, cache tables are created in the TimesTen database that correspond to the Oracle Database tables being cached.

A separate table definition must be specified in the cache group definition for each Oracle Database table that is being cached. The owner, table name, and cached column names of a TimesTen cache table must match the owner, table name, and column names of the corresponding cached Oracle Database table. The cache table can contain all or a subset of the columns and rows of the cached Oracle Database table. Each TimesTen cache table must have a primary key.

Before you define the cache group table, create the Oracle Database tables that are to be cached. Each table should be either:

- An Oracle Database table with a primary key on non-nullable columns. The TimesTen cache table primary key must be defined on the full Oracle Database table primary key. For example, if the cached Oracle Database table has a composite primary key on columns c1, c2 and c3, the TimesTen cache table must also have a composite primary key on columns c1, c2 and c3.
The following example shows how to create a cache group from an Oracle Database table with a composite primary key. Create the job_history table with a composite key on the Oracle database:

SQL> CREATE TABLE job_history
(employee_id NUMBER(6) NOT NULL,
start_date DATE NOT NULL,
end_date DATE NOT NULL,
job_id VARCHAR2(10) NOT NULL,
department_id NUMBER(4),
PRIMARY KEY(employee_id, start_date));
Table created.

Create the cache group on TimesTen with all columns of the composite primary key:

Command> CREATE WRITETHROUGH CACHE GROUP job_hist_cg
> FROM oratt.job_history
> (employee_id NUMBER(6) NOT NULL,
> start_date DATE NOT NULL,
> end_date DATE NOT NULL,
> job_id VARCHAR2(10) NOT NULL,
> department_id NUMBER(4),
> PRIMARY KEY(employee_id, start_date));

- An Oracle Database table with non-nullable columns upon which a unique index is defined on one or more of the non-nullable columns in the table. The TimesTen cache table primary key must be defined on all of the columns in the unique index. For example, if the unique index for the Oracle Database table is made up of multiple columns c1, c2, and c3, the TimesTen cache table must have a composite primary key on columns c1, c2, and c3.
The following examples create Oracle Database unique indexes defined on tables with non-nullable columns.

SQL> CREATE TABLE regions(
region_id NUMBER NOT NULL,
region_name VARCHAR2(25));
Table created.
SQL> CREATE UNIQUE INDEX region_idx
ON regions(region_id);
Index created.

SQL> CREATE TABLE sales(
prod_id INT NOT NULL,
cust_id INT NOT NULL,
quantity_sold INT NOT NULL,
time_id DATE NOT NULL);
Table created.
SQL> CREATE UNIQUE INDEX sales_index ON sales(prod_id, cust_id);
Index created.

After creation of the Oracle Database table and unique index, you can create cache groups on TimesTen for these tables using the unique index columns as the primary key definition as shown below:

Command> CREATE WRITETHROUGH CACHE GROUP region_cg
> FROM oratt.regions
> (region_id NUMBER NOT NULL PRIMARY KEY,
>  region_name VARCHAR2(25));

Command> CREATE WRITETHROUGH CACHE GROUP sales_cg
> FROM oratt.sales
> (prod_id INT NOT NULL, cust_id INT NOT NULL,
>  quantity_sold INT NOT NULL, time_id DATE NOT NULL,
>  PRIMARY KEY(prod_id, cust_id));

A TimesTen database can contain multiple cache groups. A cache group can contain one or more cache tables. An Oracle Database table cannot be cached in more than one cache group within the same TimesTen database.

Creating indexes on a cache table in TimesTen can help speed up particular queries issued on the table in the same fashion as on a TimesTen regular table. You can create non-unique indexes on a TimesTen cache table. Do not create unique indexes on a cache table that do not match any unique index on the cached Oracle Database table. Otherwise, it can cause unique constraint failures in the cache table that do not occur in the cached Oracle Database table, and result in these tables in the two databases being no longer synchronized with each other when autorefresh operations are performed.

Single-table cache group

The simplest cache group is one that caches a single Oracle Database table. In a single-table cache group, there is a root table but no child tables.

Figure 4-1 shows a single-table cache group target_customers that caches the customer table.

Figure 4-1 Cache group with a single table

Multiple-table cache group

A multiple-table cache group is one that defines a root table and one or more child tables. A cache group can only contain one root table. Each child table must reference the primary key or a unique index of the root table or of another child table in the cache group using a foreign key constraint. Although tables in a multiple-table cache group must be related to each other in the TimesTen database through foreign key constraints, it is not required that the tables be related to each other in the Oracle database. The root table does not reference any table in the cache group with a foreign key constraint.

Figure 4-2 shows a multiple-table cache group customer_orders that caches the customer, orders and order_item tables. Each parent table in the customer_orders cache group has a primary key that is referenced by a child table through a foreign key constraint. The customer table is the root table of the cache group because it does not reference any table in the cache group with a foreign key constraint. The primary key of the root table is considered the primary key of the cache group. The orders table is a child table of the customer root table. The order_item table is a child table of the orders child table.

Figure 4-2 Cache group with multiple tables

The table hierarchy in a multiple-table cache group can designate child tables to be parents of other child tables. A child table cannot reference more than one parent table. However, a parent table can be referenced by more than one child table.

Figure 4-3 shows an improper cache table hierarchy. Neither the customer nor the product table references a table in the cache group with a foreign key constraint. This results in the cache group having two root tables which is invalid.

Figure 4-3 Problem: Cache group contains two root tables

To resolve this problem and cache all the tables, create a cache group which contains the customer, orders, and order_item tables, and a second cache group which contains the product and the inventory tables as shown in Figure 4-4.

Figure 4-4 Solution: Create two cache groups

Creating a cache group

You create cache groups by using a CREATE CACHE GROUP SQL statement or by using Oracle SQL Developer, a graphical tool. For more information about SQL Developer, see Oracle SQL Developer Oracle TimesTen In-Memory Database Support User's Guide.

Cache groups are identified as either system managed or user managed. System managed cache groups enforce specific behaviors, while the behavior of a user managed cache group can be customized. System managed cache group types include:

- Read-only cache group

- Asynchronous writethrough (AWT) cache group

- Synchronous writethrough (SWT) cache group

See "User managed cache group" for information about user managed cache groups.

The following topics also apply to creating a cache group:

- AUTOREFRESH cache group attribute

- Using a WHERE clause

- ON DELETE CASCADE cache table attribute

- UNIQUE HASH ON cache table attribute

Cache groups must be created by and are owned by the cache manager user.

You cannot cache Oracle Database data in a temporary database.

Read-only cache group

A read-only cache group enforces a caching behavior where the TimesTen cache tables cannot be updated directly, and committed updates on the cached Oracle Database tables are automatically refreshed to the cache tables as shown in Figure 4-5.

Figure 4-5 Read-only cache group

If the TimesTen database is unavailable for whatever reason, you can still update the Oracle Database tables that are cached in a read-only cache group. When the TimesTen database returns to operation, updates that were committed on the cached Oracle Database tables while the TimesTen database was unavailable are automatically refreshed to the TimesTen cache tables.

Note:
When TimesTen manages operations for read only cache groups, it connects to the Oracle database using the cache administration user name and password set with the ttCacheUidPwdSet built-in procedure. For more details on ttCacheUidPwdSet, see "Set the cache administration user name and password".

The following are the definitions of the Oracle Database tables that are to be cached in the read-only cache groups that are defined in Example 4-1, Example 4-12, Example 4-13, Example 4-21 and Example 4-22. The Oracle Database tables are owned by the schema user oratt. The oratt user must be granted the CREATE SESSION and RESOURCE privileges before it can create tables.

CREATE TABLE customer
(cust_num NUMBER(6) NOT NULL PRIMARY KEY,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100));

CREATE TABLE orders
(ord_num      NUMBER(10) NOT NULL PRIMARY KEY,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL);

The companion Oracle Database user with the same name as the TimesTen cache manager user must be granted the SELECT privilege on the oratt.customer and oratt.orders tables in order for the cache manager user to create a read-only cache group that caches these tables, and for autorefresh operations to occur from the cached Oracle Database tables to the TimesTen cache tables.

Use the CREATE READONLY CACHE GROUP statement to create a read-only cache group.

Example 4-1 Creating a read-only cache group

The following statement creates a read-only cache group customer_orders that caches the tables oratt.customer (root table) and oratt.orders (child table):

CREATE READONLY CACHE GROUP customer_orders
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num)),
oratt.orders
(ord_num      NUMBER(10) NOT NULL,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL,
PRIMARY KEY(ord_num),
FOREIGN KEY(cust_num) REFERENCES oratt.customer(cust_num));

The cache tables in a read-only cache group cannot be updated directly. However, you can set the passthrough level to 2 to allow committed update operations issued on a TimesTen cache table to be passed through and processed on the cached Oracle Database table, and then have the updates be automatically refreshed into the cache table. See "Setting a passthrough level".

The effects of a passed through statement on cache tables in a read-only cache group do not occur in the transaction in which the update operation was issued. Instead, they are seen after the passed through update operation has been committed on the Oracle database and the next automatic refresh of the cache group has occurred. The companion Oracle Database user of the TimesTen cache manager user must be granted the INSERT, UPDATE and DELETE privileges on the Oracle Database tables that are cached in the read-only cache group in order for the passed through update operations to be processed on the cached Oracle Database tables.

If you manually created the Oracle Database objects used to enforce the predefined behaviors of an autorefresh cache group as described in "Manually create Oracle Database objects used to manage data caching", you need to set the autorefresh state to OFF when creating the cache group.

Then you need to run the ttIsql utility's cachesqlget command to generate a SQL*Plus script used to create a log table and a trigger in the Oracle database for each Oracle Database table that is cached in the read-only cache group. See "Manually creating Oracle Database objects for autorefresh cache groups" for information about how to create these objects.

Restrictions with read-only cache groups

The following restrictions apply when using a read-only cache group:

- The cache tables on TimesTen cannot be updated directly.

- Only the ON DELETE CASCADE and UNIQUE HASH ON cache table attributes can be used in the cache table definitions.
See "ON DELETE CASCADE cache table attribute" for more information about the ON DELETE CASCADE cache table attribute.

See "UNIQUE HASH ON cache table attribute" for more information about the UNIQUE HASH ON cache table attribute.

- A FLUSH CACHE GROUP statement cannot be issued on the cache group.
See "Flushing a user managed cache group" for more information about the FLUSH CACHE GROUP statement.

- A TRUNCATE TABLE statement issued on a cached Oracle Database table is not automatically refreshed to the TimesTen cache table.

- A LOAD CACHE GROUP statement can only be issued on the cache group if the cache tables are empty, unless the cache group is dynamic.
See "Loading and refreshing a cache group" for more information about the LOAD CACHE GROUP statement.

See "Dynamic cache groups" for more information about dynamic cache groups.

- The autorefresh state must be PAUSED before you can issue a LOAD CACHE GROUP statement on the cache group, unless the cache group is dynamic, in which case the autorefresh state must be PAUSED or ON. The LOAD CACHE GROUP statement cannot contain a WHERE clause, unless the cache group is dynamic, in which case the WHERE clause must be followed by a COMMIT EVERY n ROWS clause.
See "AUTOREFRESH cache group attribute" for more information about autorefresh states.

See "Using a WHERE clause" for more information about WHERE clauses in cache group definitions and operations.

- The autorefresh state must be PAUSED before you can issue a REFRESH CACHE GROUP statement on the cache group. The REFRESH CACHE GROUP statement cannot contain a WHERE clause.
See "Loading and refreshing a cache group" for more information about the REFRESH CACHE GROUP statement.

- All tables and columns referenced in WHERE clauses when creating, loading or unloading the cache group must be fully qualified. For example:
user_name.table_name and user_name.table_name.column_name

- Least recently used (LRU) aging cannot be specified on the cache group, unless the cache group is dynamic where LRU aging is defined by default.
See "LRU aging" for more information about LRU aging.

- Read-only cache groups cannot cache Oracle Database views or materialized views.

Asynchronous writethrough (AWT) cache group

An asynchronous writethrough (AWT) cache group enforces a caching behavior where committed updates on the TimesTen cache tables are automatically and asynchronously propagated to the cached Oracle Database tables as shown in Figure 4-6.

Note:
You should avoid executing DML statements on Oracle Database tables cached in an AWT cache group. This can result in an error condition. For more information, see "Restrictions with AWT cache groups".

Figure 4-6 Asynchronous writethrough cache group

Since an AWT cache group propagates data from the TimesTen database to the Oracle database, any data modified by the user in the cached tables on the Oracle database is not automatically uploaded from the Oracle database to the TimesTen database. In this case, you must explicitly unload and then reload the AWT cache groups on TimesTen.

The transaction commit on the TimesTen database occurs asynchronously from the commit on the Oracle database. This enables an application to continue issuing transactions on the TimesTen database without waiting for the Oracle Database transaction to complete. However, your application cannot ensure when the transactions are completed on the Oracle database.

Execution of the UNLOAD CACHE GROUP statement for an AWT cache group waits until updates on the rows have been propagated to the Oracle database.

You can update cache tables in an AWT cache group even if the Oracle database is unavailable. When the Oracle database returns to operation, updates that were committed on the cache tables while the Oracle database was unavailable are automatically propagated to the cached Oracle Database tables.

If there are updates from DML statements that you do not want propagated to the Oracle database, then you can disable propagation of committed updates (as a result of executing DML statements) within the current transaction to the Oracle database by setting the flag in the ttCachePropagateFlagSet built-in procedure to zero. After the flag is set to zero, the effects of executing any DML statements are never propagated to the back-end Oracle database. Thus, these updates exist only on the TimesTen database. You can then re-enable propagation by resetting the flag to one with the ttCachePropagateFlagSet built-in procedure. After the flag is set back to one, propagation of all committed updates to the Oracle database resumes. The propagation flag automatically resets to one after the transaction is committed or rolled back. See "ttCachePropagateFlagSet" in the Oracle TimesTen In-Memory Database Reference for more details.

Note:
When TimesTen manages operations for AWT cache groups, it connects to the Oracle database using the cache administration user name and password set with the ttCacheUidPwdSet built-in procedure. For more details on ttCacheUidPwdSet, see "Set the cache administration user name and password".

The following is the definition of the Oracle Database table that is to be cached in the AWT cache groups that are defined in Example 4-2, Example 4-14 and Example 4-16. The Oracle Database table is owned by the schema user oratt. The oratt user must be granted the CREATE SESSION and RESOURCE privileges before it can create tables.

CREATE TABLE customer
(cust_num NUMBER(6) NOT NULL PRIMARY KEY,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100));

The companion Oracle Database user of the TimesTen cache manager user must be granted the SELECT privilege on the oratt.customer table in order for the cache manager user to create an AWT cache group that caches this table. The cache administration user must be granted the INSERT, UPDATE and DELETE Oracle Database privileges on the oratt.customer table for asynchronous writethrough operations to be applied to the Oracle Database.

Use the CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP statement to create an AWT cache group.

Example 4-2 Creating an AWT cache group

The following statement creates an asynchronous writethrough cache group new_customers that caches the oratt.customer table:

CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP new_customers
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num));

The following sections describe configuration, behavior, and management for AWT cache groups:

- Managing the replication agent

- Configuring parallel propagation to Oracle Database tables

- What an AWT cache group does and does not guarantee

- Restrictions with AWT cache groups

- Reporting Oracle Database permanent errors for AWT cache groups

Managing the replication agent

Performing asynchronous writethrough operations requires that the replication agent be running on the TimesTen database that contains AWT cache groups. Executing a CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP statement creates a replication scheme that enables committed updates on the TimesTen cache tables to be asynchronously propagated to the cached Oracle Database tables.

After you have created AWT cache groups, start the replication agent on the TimesTen database.

Example 4-3 Starting the replication agent

The replication agent can be manually started programmatically by calling the ttRepStart built-in procedure as the cache manager user:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> call ttRepStart;

It can also be started from a command line by running a ttAdmin -repStart utility command as a TimesTen external user with the CACHE_MANAGER privilege:

% ttAdmin -repStart cachealone1

The replication agent does not start unless there is at least one AWT cache group or replication scheme in the TimesTen database.

If the replication agent is running, it must be stopped before you can issue another CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP statement or a DROP CACHE GROUP statement on an AWT cache group.

Example 4-4 Stopping the replication agent

The replication agent can be manually stopped programmatically by calling the ttRepStop built-in procedure as the cache manager user:

Command> call ttRepStop;

It can also be stopped from a command line by running a ttAdmin -repStop utility command as a TimesTen external user with the CACHE_MANAGER privilege:

% ttAdmin -repStop cachealone1

You can set a replication agent start policy to determine how and when the replication agent process starts on a TimesTen database.

The default start policy is manual which means the replication agent must be started manually by calling the ttRepStart built-in procedure or running a ttAdmin -repStart utility command. To manually stop a running replication agent process, call the ttRepStop built-in procedure or run a ttAdmin -repStop utility command.

The start policy can be set to always so that the replication agent starts automatically when the TimesTen main daemon process starts. With the always start policy, the replication agent cannot be stopped when the main daemon is running unless the start policy is changed to either manual or norestart and then a manual stop is issued by calling the ttRepStop built-in procedure or running a ttAdmin -repStop utility command.

With the manual and always start policies, the replication agent automatically restarts after a failure such as a database invalidation.

The start policy can be set to norestart which means the replication agent must be started manually by calling the ttRepStart built-in procedure or running a ttAdmin -repStart utility command, and stopped manually by calling the ttRepStop built-in procedure or running a ttAdmin -repStop utility command.

With the norestart start policy, the replication agent does not automatically restart after a failure such as a database invalidation. You must restart the replication agent manually by calling the ttRepStart built-in procedure or running a ttAdmin -repStart utility command.

Example 4-5 Setting a replication agent start policy

As the instance administrator, grant the ADMIN privilege to the cache manager user:

% ttIsql cachealone1
Command> GRANT ADMIN TO cacheuser;
Command> exit

The replication agent start policy can be set programmatically by calling the ttRepPolicySet built-in procedure as the cache manager user:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> call ttRepPolicySet('manual');
Command> exit

It can also be set from a command line by running a ttAdmin -repPolicy utility command as a TimesTen external user with the ADMIN privilege:

% ttAdmin -repPolicy always cachealone1

Since the AWT cache group uses the replication agent to asynchronously propagate transactions to the Oracle database, these transactions remain in the transaction log buffer and transaction log files until the replication agent confirms they have been fully processed by the Oracle database. You can monitor the propagation for these transactions with the ttLogholds built-in procedure. When you call the ttLogHolds built-in procedure, the description field contains "_ORACLE" to identify the transaction log hold for the AWT cache group propagation.

Command> call ttLogHolds();
< 0, 18958336, Checkpoint                    , cachealone1.ds0 >
< 0, 19048448, Checkpoint                    , cachealone1.ds1 >
< 0, 19050904, Replication                   , ADC6160529:_ORACLE >
3 rows found.

For more details on the ttLogHolds built-in procedure and how to monitor replication through bookmarks and log sequence numbers, see the "Show replicated log holds" section in the Oracle TimesTen In-Memory Database Replication Guide.

Configuring parallel propagation to Oracle Database tables

To improve throughput for an AWT cache group, you can configure multiple threads that act in parallel to propagate and apply transactional changes to the Oracle database. Parallel propagation enforces transactional dependencies and applies changes in AWT cache tables to Oracle Database tables in commit order.

Parallel propagation is supported for AWT cache groups with the following configurations:

- AWT cache groups in a cache grid

- AWT cache groups involved in an active standby pair replication scheme

- AWT cache groups in a single TimesTen database (without a replication scheme configuration)

- AWT cache groups configured with any aging policy

The following data store attributes enable parallel propagation and control the number of threads that operate in parallel to propagate changes from AWT cache tables to the corresponding Oracle Database tables:

- ReplicationApplyOrdering enables parallel propagation by default.

- ReplicationParallelism defines the number of transmitter threads on the source database and the number of receiver threads on the target database for parallel replication in a replication scheme. This value can be between 2 and 32 when used solely for parallel replication. The default is 1. In addition, the value of ReplicationParellelism cannot exceed half the value of LogBufParallelism.

- CacheAWTParallelism, when set, determines the number of threads used in parallel propagation of changes from AWT cache tables to the Oracle Database tables. Set this attribute to a number from 2 to 31. The default is 1.

Parallel propagation for an AWT cache group is configured with one of the following scenarios:

- ReplicationApplyOrdering is set to 0 and ReplicationParallelism is greater than 1.
If you do not set CacheAWTParallelism, the number of threads that apply changes to Oracle Database is 2 times the setting for ReplicationParallelism. For example, if ReplicationParallelism=3, the number of threads that apply changes to Oracle Database tables is 6. In this case, ReplicationParallelism can only be set from 2 to 16; otherwise, twice the value would exceed the maximum number of 31 threads for parallel propagation. If the value is set to 16, the maximum number of threads defaults to 31.

- ReplicationApplyOrdering is set to 0, ReplicationParallelism is equal to or greater than 1, and CacheAWTParallelism is greater than 1. The value for CacheAWTParallelism must be greater than or equal to the value set for ReplicationParallelism and less than or equal to 31.
If CacheAWTParallelism is not specified, then ReplicationParallelism is used to determine the number of threads that are used for parallel propagation to Oracle Database. However, since this value is doubled for parallel propagation threads, you can only set ReplicationParallelism to a number from 2 to 16. If the value is set to 16, the maximum number of threads defaults to 31.

If both ReplicationParallelism and CacheAWTParallelism attributes are set, the value set in CacheAWTParallelism configures the number of threads used for parallel propagation. The setting for CacheAWTParallelism determines the number of apply threads for parallel propagation and the setting for ReplicationParallelism determines the number of threads for parallel replication. Thus, if ReplicationParallelism is set to 4 and CacheAWTParallelism is set to 6, then the number of threads that apply changes to Oracle Database tables is 6. This enables the number of threads used to be different for parallel replication and parallel propagation to Oracle Database tables.

Note:
For more information about parallel replication, see "Configuring parallel replication" in the Oracle TimesTen In-Memory Database Replication Guide.
For more details on these data store attributes, see "ReplicationApplyOrdering," "ReplicationParallelism," and "CacheAWTParallelism" in the Oracle TimesTen In-Memory Database Reference.

These data store attributes are interrelated. Table 4-1 shows the result with the combination of the various possible attribute values.

Table 4-1 Results of Parallel Propagation Data Store Attribute Relationships

ReplicationApply Ordering

ReplicationParallelism

CacheAWTParallelism

Number of parallel propagation threads

Set to 0, which enables parallel propagation

Set to > 1 for multiple tracks and <= 16.

Not specified.

Set to twice the value of ReplicationParallelism.

Set to 0, which enables parallel propagation

Set to > 16 and <= 32 for multiple tracks.

Not specified.

Error is thrown. If CacheAWTParallelism is not set, then 2 times the value set in ReplicationParallelism specifies the number of threads. Thus, in this case, ReplicationParallelism cannot be greater than 16.

Set to 0, which enables parallel propagation

Set to > 1 and <= 32 for multiple tracks.

Set to >= to ReplicationParallelism.

Set to number specified by CacheAWTParallelism.

Set to 0, which enables parallel propagation

Set to > 1 and <= 32 for multiple tracks.

Set to < ReplicationParallelism.

Error is thrown at database creation. The CacheAWTParallelism must be set to a value greater than or equal to ReplicationParallelism.

Set to 0, which enables parallel propagation

Set to 1 or not specified. Single track.

Set to > 1

Set to number specified by CacheAWTParallelism.

Set to 1, which disables parallel propagation.

N/A

Set to > 1

Error is thrown at database creation, since parallelism is turned off, but CacheAWTParallelism is set to a value, expecting parallel propagation to be enabled.

Foreign keys in Oracle Database tables that are to be cached must have indexes created on the foreign keys. Consider these Oracle Database tables:

CREATE TABLE parent (c1 NUMBER PRIMARY KEY NOT NULL);
CREATE TABLE child (c1 NUMBER PRIMARY KEY NOT NULL,
c2 NUMBER REFERENCES parent(c1));
CREATE TABLE grchild (c1 NUMBER PRIMARY KEY NOT NULL,
c2 NUMBER REFERENCES parent(c1),
c3 NUMBER REFERENCES parent(c1));

These indexes must be created:

CREATE INDEX idx_1 ON child(c2);
CREATE INDEX idx_2 ON grchild(c2);
CREATE INDEX idx_3 ON grchild(c3);

Table constraint restrictions when using parallel propagation for AWT cache groups

When you use parallel propagation for AWT cache groups, you must manually enforce data consistency. Any unique index, unique constraint, or foreign key constraint that exists on columns in the Oracle Database tables that are to be cached should also be created on the AWT cache tables within TimesTen. If you cannot create these constraints on the AWT cache tables and you have configured for parallel propagation, then TimesTen serializes any transactions with DML operations to any table with missing constraints. For example, if a unique index created on a table in the Oracle database cannot be created on the corresponding cached table in TimesTen, all transactions for this table are serialized.

TimesTen automatically checks for missing constraints on the Oracle database that are not cached on TimesTen when you issue any of the following SQL statements:

- When you create an AWT cache group with the CREATE ASYNCHRONOUS CACHE GROUP statement

- When you create a unique index on an AWT cache table with the CREATE UNIQUE INDEX statement

- When you drop a unique index on an AWT cache table with the DROP INDEX statement

Note:
You can manually initiate a check for missing constraints with the ttCacheCheck built-in procedure. For example, TimesTen does not automatically check for missing constraints after a schema change on cached Oracle Database tables. After any schema change on the Oracle database, you should perform an manual check for missing constraints by executing ttCacheCheck on the TimesTen database.
See "Manually initiate check for missing constraints" for other conditions where you should manually check for missing constraints.

If the check notes missing constraints on the cached tables, TimesTen issues warnings about each missing constraint.

For the following scenarios, the cached table is marked so that transactions that include DML operations are serialized when propagated to the Oracle database.

- Transactions that apply DML operations to AWT cache tables that are missing unique indexes or unique constraints.

- Missing foreign key constraints for tables within a single AWT cache group.

- If both the referencing table and the referenced table for the foreign key relationship are in the same AWT cache group and the foreign key relationship is not defined, both tables are marked for transaction serialization.

- If the referencing table is in an AWT cache group and the referenced table is not in an AWT cache group, the table inside the cache group is not marked for transaction serialization. Only a warning is issued to notify the user of the missing constraint.

- If the referenced table is in an AWT cache group and the referencing table is not in an AWT cache group, the table inside the cache group is not marked for transaction serialization. Only a warning is issued to notify the user of the missing constraint.

- Missing foreign key constraints between cache groups. When you have tables defined in separate AWT cache groups that are missing a foreign key constraint, both tables are marked for serialized transactions.

- If a missing foreign key constraint causes a chain of foreign key constraints to be broken between two AWT cache groups, transactions for all tables within both AWT cache groups are serialized.

Note:
An Oracle Database trigger may introduce an operational dependency of which TimesTen may not be aware. In this case, you should either disable parallel propagation for the AWT cache group or do not cache the table in an AWT cache group on which the trigger is created.

Example 4-6 Examples of missing constraints when creating an AWT cache group

The following example creates two tables in the oratt schema in the Oracle database. There is a foreign key relationship between active_customer and the ordertab tables. Because the examples use these tables for parallel propagation, an index is created on the foreign key in the ordertab table.

SQL> CREATE TABLE active_customer
(custid NUMBER(6) NOT NULL PRIMARY KEY,
name VARCHAR2(50),
addr VARCHAR2(100),
zip VARCHAR2(12),
region VARCHAR2(12) DEFAULT 'Unknown');
Table created.

SQL> CREATE TABLE ordertab
(orderid NUMBER(10) NOT NULL PRIMARY KEY,
custid NUMBER(6) NOT NULL);
Table created.

SQL> ALTER TABLE ordertab
ADD CONSTRAINT cust_fk
FOREIGN KEY (custid) REFERENCES active_customer(custid);
Table altered.

SQL> CREATE INDEX order_idx on ordertab (custid);

TimesTen automatically checks for missing constraints when each CREATE CACHE GROUP is issued. In the following example, a single cache group is created that includes the active_customer table. Only a warning is issued since the active_customer is the referenced table and the referencing table, ordertab, is not in any AWT cache group. The active_customer table is not marked for serialized transactions.

CREATE WRITETHROUGH CACHE GROUP update_cust
FROM oratt.active_customer
(custid NUMBER(6) NOT NULL PRIMARY KEY,
name VARCHAR2(50),
addr VARCHAR2(100),
zip VARCHAR2(12));
Warning  5297: The following Oracle foreign key constraints on AWT cache table
ORATT.ACTIVE_CUSTOMER contain cached columns that do not have corresponding
foreign key constraints on TimesTen: ORATT.CUST_FK [Outside of CG].

The following example creates two AWT cache groups on TimeTen, one that includes the active_customer table and the other includes the ordertab table. There is a missing foreign key constraint between the cache groups. Thus, a warning is issued for both tables, but only the ordertab table is marked for serial transactions since it is the referencing table that should contain the foreign key.

CREATE WRITETHROUGH CACHE GROUP update_cust
FROM oratt.active_customer
(custid NUMBER(6) NOT NULL PRIMARY KEY,
name VARCHAR2(50),
addr VARCHAR2(100),
zip VARCHAR2(12);
Warning  5297: The following Oracle foreign key constraints on AWT cache table
oratt.update_customer contain cached columns that do not have corresponding
foreign key constraints on TimesTen: ordertab.cust_fk [Outside of CG].

CREATE WRITETHROUGH CACHE GROUP update_orders
FROM oratt.ordertab
(orderid NUMBER(10) NOT NULL PRIMARY KEY,
custid NUMBER(6) NOT NULL);
Warning  5295: Propagation will be serialized on AWT cache table
ORATT.ORDERTAB because the following Oracle foreign key constraints on this
table contain cached columns that do not have corresponding foreign key
constraints on TimesTen: ORDERTAB.CUST_FK [Across AWT cache groups].

Manually initiate check for missing constraints

The ttCacheCheck built-in procedure performs the same check for missing constraints for cached tables on the Oracle database as performed automatically by TimesTen. The ttCacheCheck provides appropriate messages about missing constraints and the tables marked for serialized propagation. With the ttCacheCheck built-in procedure, you can check for missing constraints for a given cache group or for all cache groups in TimesTen to ensure that all cache groups are not missing constraints.

Note:
Since ttCacheCheck updates system tables to indicate if DML executed against a table should or should not be serialized, you must commit or roll back after the ttCacheCheck built-in completes.
For more details of the ttCacheCheck built-in procedure, see "ttCacheCheck" in the Oracle TimesTen In-Memory Database Reference.

You may need to manually call the ttCacheCheck built-in procedure to update the known dependencies after any of the following scenarios:

- After dropping a series of AWT cache groups on TimesTen with the DROP CACHE GROUP statement.

- After adding or dropping a unique index, unique constraint, or foreign key on an Oracle Database table that is cached in an AWT cache group. If you do not call the ttCacheCheck built-in procedure after adding a constraint, you may receive a run time error on the AWT cache group. After dropping a constraint, TimesTen may serialize transactions even if it is not necessary. Calling the ttCacheCheck built-in procedure verifies whether serialization is necessary.

- You can use this built-in procedure to determine why some transactions are being serialized.

Note:
The ttCacheCheck built-in procedure cannot be called while the replication agent is running.
If a DDL statement is being executed on an AWT cache group when ttCacheCheck is called, then ttCacheCheck waits for the statement to complete or until the timeout period is reached.

If you have not defined the CacheAwtParallelism data store attribute to greater than one or the specified cache group is not an AWT cache group, then the ttCacheCheck built-in procedure returns an empty result set.

Example 4-7 Manually executing ttCacheCheck update missing dependencies

The following example shows the user manually executing the ttCacheCheck built-in procedure to determine if there are any missing constraints for an AWT cache group update_orders that is owned by cacheuser. A result set is returned that includes the error message. The ordertab table in the update_orders cache group is marked for serially propagated transactions.

Command> call ttCacheCheck(NULL, 'cacheuser', 'update_orders');

< CACHEUSER, UPDATE_ORDERS, CACHEUSER, ORDERTAB, Foreign Key, CACHEUSER,
CUST_FK, 1, Transactions updating this table will be serialized to Oracle
because: The missing foreign key connects two AWT cache groups.,
table CACHEUSER.ORDERTAB constraint CACHEUSER.CUST_FK foreign key(CUSTID)
references CACHEUSER.ACTIVE_CUSTOMER(CUSTID) >
1 row found.

Whenever the cache group schema changes in either the TimesTen or Oracle databases, you can call ttCacheCheck against all AWT cache groups to verify all constraints. The following example shows the user manually executing the ttCacheCheck built-in procedure to determine if there are any missing constraints for any AWT cache group in the entire TimesTen database by providing a NULL value for all input parameters. A result set is returned that includes any error messages.

Command> call ttCacheCheck(NULL, NULL, NULL);

< CACHEUSER, UPDATE_ORDERS, CACHEUSER, ORDERTAB, Foreign Key, CACHEUSER,
CUST_FK, 1, Transactions updating this table will be serialized to Oracle
because: The missing foreign key connects two AWT cache groups.,
table CACHEUSER.ORDERTAB constraint CACHEUSER.CUST_FK foreign key(CUSTID)
references CACHEUSER.ACTIVE_CUSTOMER(CUSTID) >
1 row found.

Configuring batch size for parallel propagation for AWT cache groups

When using AWT cache groups, TimesTen batches together one or more transactions that are to be applied in parallel to the back-end Oracle database. The CacheParAwtBatchSize parameter configures a threshold value for the number of rows included in a single batch. Once the maximum number of rows is reached, TimesTen includes the rest of the rows in the transaction (TimesTen does not break up any transactions), but does not add any more transactions to the batch.

For example, a user sets the CacheParAwtBatchSize to 200. For the next AWT propagation, there are three transactions, each with 120 rows, that need to be propagated and applied to the Oracle database. TimesTen includes the first two transactions in the first batch for a total of 240 rows. The third transaction is included in a second batch.

The default value for the CacheParAwtBatchSize parameter is 125 rows. The minimum value is 1. For more details on the CacheParAwtBatchSize parameter in the ttDBConfig built-in procedure, see "ttDBConfig" in the Oracle TimesTen In-Memory Database Reference.

You can retrieve the current value of CacheParAwtBatchSize as follows:

call ttDBConfig('CacheParAwtBatchSize');
< CACHEPARAWTBATCHSIZE, 125 >
1 row found.

You can set the CacheParAwtBatchSize parameter to 200 as follows:

call ttDBConfig('CacheParAwtBatchSize','200');
< CACHEPARAWTBATCHSIZE, 200 >
1 row found

Set the CacheParAwtBatchSize parameter only when advised by Oracle Support, who analyzes the workload and any dependencies in the workload to determine if a different value for CacheParAwtBatchSize could improve performance. Dependencies exist when transactions concurrently change the same data. Oracle Support may advise you to reduce this value if there are too many dependencies in the workload.

What an AWT cache group does and does not guarantee

An AWT cache group can guarantee that:

- No transactions are lost because of communication failures between the TimesTen and Oracle databases.

- If the replication agent is not running or loses its connection to the Oracle database, automatic propagation of committed updates on the TimesTen cache tables to the cached Oracle Database tables resumes after the agent restarts or reconnects to the Oracle database.

- Transactions are committed in the Oracle database in the same order they were committed in the TimesTen database.

An AWT cache group cannot guarantee that:

- All transactions committed successfully in the TimesTen database are successfully propagated to and committed in the Oracle database. Execution errors on the Oracle database cause the transaction in the Oracle database to be rolled back. For example, an update on the Oracle database may fail because of a unique constraint violation. Transactions that contain execution errors are not retried.
Execution errors are considered permanent errors and are reported to the TimesTenDatabaseFileName.awterrs file that resides in the same directory as the TimesTen database's checkpoint files. See "Reporting Oracle Database permanent errors for AWT cache groups" for more information.

- The absolute order of Oracle Database updates is preserved because TimesTen does not resolve update conflicts. The following are some examples:

- In two separate TimesTen databases (DB1 and DB2), different AWT cache groups cache the same Oracle Database table. An update is committed on the cache table in DB1. An update is then committed on the cache table in DB2. The two cache tables reside in different TimesTen databases and cache the same Oracle Database table. Because the writethrough operations are asynchronous, the update from DB2 may get propagated to the Oracle database before the update from DB1, resulting in the update from DB1 overwriting the update from DB2.
Using a dynamic AWT global cache group resolves this write inconsistency. See "Global cache groups" for more information about global cache groups.

- An update is committed on a cache table in an AWT cache group. The same update is committed on the cached Oracle Database table using a passthrough operation. The cache table update, which is automatically and asynchronously propagated to the Oracle database, may overwrite the passed through update that was processed directly on the cached Oracle Database table depending on when the propagated update and the passed through update is processed on the Oracle database. For this and other potential error conditions, TimesTen recommends that you do not execute DML statements directly against Oracle Database tables cached in an AWT cache group. For more information, see "Restrictions with AWT cache groups".

Restrictions with AWT cache groups

The following restrictions apply when using an AWT cache group:

- Only the ON DELETE CASCADE and UNIQUE HASH ON cache table attributes can be used in the cache table definitions.
See "ON DELETE CASCADE cache table attribute" for more information about the ON DELETE CASCADE cache table attribute.

See "UNIQUE HASH ON cache table attribute" for more information about the UNIQUE HASH ON cache table attribute.

- A FLUSH CACHE GROUP statement cannot be issued on the cache group.
See "Flushing a user managed cache group" for more information about the FLUSH CACHE GROUP statement.

- The cache table definitions cannot contain a WHERE clause.
See "Using a WHERE clause" for more information about WHERE clauses in cache group definitions and operations.

- A TRUNCATE TABLE statement cannot be issued on the cache tables.

- AWT cache groups cannot cache Oracle Database views or materialized views.

- The replication agent must be stopped before creating or dropping an AWT cache group.
See "Managing the replication agent" for information about how to stop and start the replication agent.

- Committed updates on the TimesTen cache tables are not propagated to the cached Oracle Database tables unless the replication agent is running.

- To create an AWT cache group, the length of the absolute path name of the TimesTen database cannot exceed 248 characters.

- You should avoid executing DML statements on Oracle Database tables cached in an AWT cache group. This could result in an error condition. Any insert, update, or delete operation on the cached Oracle Database table can negatively affect the operations performed on TimesTen for the affected rows. TimesTen does not detect or resolve update conflicts that occur on the Oracle database. Committed updates made directly on a cached Oracle Database table may be overwritten by a committed update made on the TimesTen cache table when the cache table update is propagated to the Oracle database. In addition, deleting rows on the cached Oracle Database table could cause an empty update if TimesTen tries to update a row that no longer exists.
To ensure that not all data is restricted from DML statements on Oracle Database, you can partition the data on Oracle Database to separate the data that is to be included in the AWT cache group from the data to be excluded from the AWT cache group.

- TimesTen performs deferred checking when determining whether a single SQL statement causes a constraint violation with a unique index.
For example, suppose there is a unique index on a cached Oracle Database table's NUMBER column, and a unique index on the same NUMBER column on the TimesTen cache table. There are five rows in the cached Oracle Database table and the same five rows in the cache table. The values in the NUMBER column range from 1 to 5.

An UPDATE statement is issued on the cache table to increment the value in the NUMBER column by 1 for all rows. The operation succeeds on the cache table but fails when it is propagated to the cached Oracle Database table.

This occurs because TimesTen performs the unique index constraint check at the end of the statement's execution after all the rows have been updated. The Oracle database, however, performs the constraint check each time after a row has been updated.

Therefore, when the row in the cache table with value 1 in the NUMBER column is changed to 2 and the update is propagated to the Oracle database, it causes a unique constraint violation with the row that has the value 2 in the NUMBER column of the cached Oracle Database table.

Reporting Oracle Database permanent errors for AWT cache groups

If transactions are not successfully propagated to and committed in the Oracle database, then the permanent errors cause the transaction in the Oracle database to be rolled back. For example, an update on the Oracle database may fail because of a unique constraint violation. Transactions that contain permanent errors are not retried.

Permanent errors are always reported to the TimesTenDatabaseFileName.awterrs text file that resides in the same directory as the TimesTen database checkpoint files. See "Oracle Database errors reported by TimesTen for AWT" in the Oracle TimesTen In-Memory Database Troubleshooting Guide for information about the contents of this file.

You can configure TimesTen to report these errors in both ASCII and XML formats with the ttCacheConfig built-in procedure.

Note:
Do not pass in any values to the tblOwner and tblName parameters for ttCacheConfig as they are not applicable to setting the format for the errors file.

- To configure TimesTen to report permanent errors to only the TimesTenDatabaseFileName.awterrs text file, call the ttCacheConfig built-in procedure with the ASCII parameter. This is the default.

Command> call ttCacheConfig('AwtErrorXmlOutput',,,'ASCII');

- To configure TimesTen to report permanent errors to both the TimesTenDatabaseFileName.awterrs text file as well as to an XML file named TimesTenDatabaseFileName.awterrs.xml, call the ttCacheConfig built-in procedure with the XML parameter.

Command> call ttCacheConfig('AwtErrorXmlOutput',,,'XML');

Note:
Before calling ttCacheConfig to direct permanent errors to the XML file, you must first stop the replication agent. Then, restart the replication agent after the built-in procedure completes.
For full details on this built-in procedure, see "ttCacheConfig" in the Oracle TimesTen In-Memory Database Reference.

When you configure error reporting to be reported in XML format, the following two files are generated when Oracle Database permanent errors occur:

- TimesTenDatabaseFileName.awterrs.xml contains the Oracle Database permanent error messages in XML format.

- TimesTenDatabaseFileName.awterrs.dtd is the file that contains the XML Document Type Definition (DTD), which is used when parsing the TimesTenDatabaseFileName.awterrs.xml file.
The XML DTD, which is based on the XML 1.0 specification, is a set of markup declarations that describes the elements and structure of a valid XML file containing a log of errors. The XML file is encoded using UTF-8. The following are the elements for the XML format.

Note:
For more information on reading and understanding XML Document Type Definitions, see http://www.w3.org/TR/REC-xml.

<!ELEMENT ttawterrorreport (awterrentry*) >
<!ELEMENT awterrentry(header, (failedop)?, failedtxn) >
<!ELEMENT header (time, datastore, oracleid, transmittingagent, errorstr,
(ctn)?, (batchid)?, (depbatchid)?) >
<!ELEMENT failedop (sql) >
<!ELEMENT failedtxn ((sql)+) >
<!ELEMENT time (hour, min, sec, year, month, day) >
<!ELEMENT hour (#PCDATA) >
<!ELEMENT min (#PCDATA) >
<!ELEMENT sec (#PCDATA) >
<!ELEMENT year (#PCDATA) >
<!ELEMENT month (#PCDATA) >
<!ELEMENT day (#PCDATA) >
<!ELEMENT datastore (#PCDATA) >
<!ELEMENT oracleid (#PCDATA) >
<!ELEMENT transmittingagent (transmitingname, pid, threadid) >
<!ELEMENT pid (#PCDATA) >
<!ELEMENT threadid (#PCDATA) >
<!ELEMENT transmittingname (#PCDATA) >
<!ELEMENT errorstr (#PCDATA) >
<!ELEMENT ctn (timestamp, seqnum) >
<!ELEMENT timestamp(#PCDATA) >
<!ELEMENT seqnum(#PCDATA) >
<!ELEMENT batchid(#PCDATA) >
<!ELEMENT depbatchid(#PCDATA) >
<!ELEMENT sql(#PCDATA) >

Synchronous writethrough (SWT) cache group

A synchronous writethrough (SWT) cache group enforces a caching behavior where committed updates on the TimesTen cache tables are automatically and synchronously propagated to the cached Oracle Database tables as shown in Figure 4-7.

Note:
You should avoid executing DML statements on Oracle Database tables cached in an SWT cache group. This can result in an error condition. For more information, see "Restrictions with SWT cache groups".

Figure 4-7 Synchronous writethrough cache group

The transaction commit on the TimesTen database occurs synchronously with the commit on the Oracle database. When an application commits a transaction in the TimesTen database, the transaction is processed in the Oracle database before it is processed in TimesTen. The application is blocked until the transaction has completed in both the Oracle and TimesTen databases.

If the transaction fails to commit in the Oracle database, the application must roll back the transaction in TimesTen. If the Oracle Database transaction commits successfully but the TimesTen transaction fails to commit, the cache tables in the SWT cache group are no longer synchronized with the cached Oracle Database tables.

Note:
The behavior and error conditions for how commit occurs on both the TimesTen and Oracle databases when committing propagated updates is the same commit process on a user managed cache group with the PROPAGATE cache attribute that is described in "PROPAGATE cache table attribute".

To manually resynchronize the cache tables with the cached Oracle Database tables, call the ttCachePropagateFlagSet built-in procedure to disable update propagation, and then reissue the transaction in the TimesTen database after correcting the problem that caused the transaction commit to fail in TimesTen. Then, call the ttCachePropagateFlagSet built-in procedure to re-enable update propagation. You can also resynchronize the cache tables with the cached Oracle Database tables by reloading the accompanying cache groups.

The following is the definition of the Oracle Database table that is to be cached in the SWT cache group that is defined in Example 4-8. The Oracle Database table is owned by the schema user oratt. The oratt user must be granted the CREATE SESSION and RESOURCE privileges before it can create tables.

CREATE TABLE product
(prod_num    VARCHAR2(6) NOT NULL PRIMARY KEY,
name        VARCHAR2(30),
price       NUMBER(8,2),
ship_weight NUMBER(4,1));

The companion Oracle Database user of the TimesTen cache manager user must be granted the SELECT privilege on the oratt.product table in order for the cache manager user to create an SWT cache group that caches this table. This Oracle Database user must also be granted the INSERT, UPDATE, and DELETE privileges on the oratt.product table for synchronous writethrough operations to occur from the TimesTen cache table to the cached Oracle Database table.

Use the CREATE SYNCHRONOUS WRITETHROUGH CACHE GROUP statement to create an SWT cache group.

Example 4-8 Creating a SWT cache group

The following statement creates a synchronous writethrough cache group top_products that caches the oratt.product table:

CREATE SYNCHRONOUS WRITETHROUGH CACHE GROUP top_products
FROM oratt.product
(prod_num    VARCHAR2(6) NOT NULL,
name        VARCHAR2(30),
price       NUMBER(8,2),
ship_weight NUMBER(4,1),
PRIMARY KEY(prod_num));

When TimesTen manages operations for SWT cache groups, it connects to the Oracle database using the current user's credentials as the user name and the OraclePwd connection attribute as the Oracle password. TimesTen does not connect to the Oracle database with the cache administration user name and password set with the ttCacheUidPwdSet built-in procedure when managing SWT cache group operations. For more details, see "Set the cache administration user name and password".

Restrictions with SWT cache groups

The following restrictions apply when using an SWT cache group:

- Only the ON DELETE CASCADE and UNIQUE HASH ON cache table attributes can be used in the cache table definitions.
See "ON DELETE CASCADE cache table attribute" for more information about the ON DELETE CASCADE cache table attribute.

See "UNIQUE HASH ON cache table attribute" for more information about the UNIQUE HASH ON cache table attribute.

- A FLUSH CACHE GROUP statement cannot be issued on the cache group.
See "Flushing a user managed cache group" for more information about the FLUSH CACHE GROUP statement

- The cache table definitions cannot contain a WHERE clause.
See "Using a WHERE clause" for more information about WHERE clauses in cache group definitions and operations.

- A TRUNCATE TABLE statement cannot be issued on the cache tables.

- SWT cache groups cannot cache Oracle Database views or materialized views.

- You should avoid executing DML statements directly on Oracle Database tables cached in an SWT cache group. This could result in an error condition. Any insert, update, or delete operation on the cached Oracle Database table can negatively affect the operations performed on TimesTen for the affected rows. TimesTen does not detect or resolve update conflicts that occur on the Oracle database. Committed updates made directly on a cached Oracle Database table may be overwritten by a committed update made on the TimesTen cache table when the cache table update is propagated to the Oracle database. In addition, deleting rows on the cached Oracle Database table could cause an empty update if TimesTen tries to update a row that no longer exists.
To ensure that not all data is restricted from DML statements on Oracle Database, you can partition the data on Oracle Database to separate the data that is to be included in the SWT cache group from the data to be excluded from the SWT cache group.

User managed cache group

If the system managed cache groups (read-only, AWT, SWT) do not satisfy your application's requirements, you can create a user managed cache group that defines customized caching behavior with one or more of the following cache table attributes:

Note:
When TimesTen manages operations for user managed cache groups, it connects to the Oracle database using the current user's credentials as the user name and the OraclePwd connection attribute as the Oracle password. TimesTen does not connect to the Oracle database with the cache administration user name and password set with the ttCacheUidPwdSet built-in procedure for user managed cache group operations. For more details, see "Set the cache administration user name and password".

- You can specify the READONLY cache table attribute on individual cache tables in a user managed cache group to define read-only behavior where the data is refreshed on TimesTen from the Oracle database at the table level.

- You can specify the PROPAGATE cache table attribute on individual cache tables in a user managed cache group to define synchronous writethrough behavior at the table level. The PROPAGATE cache table attribute specifies that committed updates on the cache table are automatically and synchronously propagated to the cached Oracle Database table.

- You can define a user managed cache group to automatically refresh and propagate committed updates between the Oracle and TimesTen databases by using the AUTOREFRESH cache group attribute and the PROPAGATE cache table attribute. Using both attributes enables bidirectional transmit, so that committed updates on the TimesTen cache tables or the cached Oracle Database tables are propagated or refreshed to each other.
See "AUTOREFRESH cache group attribute" for more information about defining an autorefresh mode, interval, and state.

- You can use the LOAD CACHE GROUP, REFRESH CACHE GROUP, and FLUSH CACHE GROUP statements to manually control the transmit of committed updates between the Oracle and TimesTen databases.
See "Loading and refreshing a cache group" for more information about the LOAD CACHE GROUP and REFRESH CACHE GROUP statements. See "Flushing a user managed cache group" for more information about the FLUSH CACHE GROUP statement.

- You can cache Oracle Database materialized views in a user managed cache group that does not use either the PROPAGATE or AUTOREFRESH cache group attributes. The cache group must be manually loaded and flushed. You cannot cache Oracle Database views.

The following sections provide more information about user managed cache groups:

- READONLY cache table attribute

- PROPAGATE cache table attribute

- Examples of user managed cache groups

READONLY cache table attribute

The READONLY cache table attribute can be specified only for cache tables in a user managed cache group. READONLY specifies that the cache table cannot be updated directly. By default, a cache table in a user managed cache group is updatable.

Unlike a read-only cache group where all of its cache tables are read-only, in a user managed cache group individual cache tables can be specified as read-only using the READONLY cache table attribute.

Example 4-10 demonstrates the READONLY cache table attribute in the oratt.cust_interests cache table.

The following restrictions apply when using the READONLY cache table attribute:

- If the cache group uses the AUTOREFRESH cache group attribute, the READONLY cache table attribute must be specified on all or none of its cache tables.
See "AUTOREFRESH cache group attribute" for more information about using the AUTOREFRESH cache group attribute.

- You cannot use both the READONLY and PROPAGATE cache table attributes on the same cache table.
See "PROPAGATE cache table attribute" for more information about using the PROPAGATE cache table attribute.

- A FLUSH CACHE GROUP statement cannot be issued on the cache group unless one or more of its cache tables use neither the READONLY nor the PROPAGATE cache table attribute.
See "Flushing a user managed cache group" for more information about the FLUSH CACHE GROUP statement.

- After the READONLY cache table attribute has been specified on a cache table, you cannot change this attribute unless you drop the cache group and re-create it.

PROPAGATE cache table attribute

The PROPAGATE cache table attribute can be specified only for cache tables in a user managed cache group. PROPAGATE specifies that committed updates on the TimesTen cache table as part of a TimesTen transaction are automatically and synchronously propagated to the cached Oracle Database table. If the PROPAGATE cache table attribute is not specified, then the default setting for a cache table in a user managed cache group is the NOT PROPAGATE cache table attribute (which does not propagate committed updates on the cache table to the cached Oracle table).

All SQL statements executed by an application on cached tables are applied to the cached tables immediately. All of these operations are buffered until the transaction commits or reaches a memory upper limit. At this time, all operations are propagated to the tables in the Oracle database.

Note:
If the TimesTen database or its daemon fails unexpectedly, the results of the transaction on either the TimesTen or Oracle databases are not guaranteed.

Since the operations in the transaction are applied to tables in both the TimesTen and Oracle databases, the process for committing is as follows:

1. After the operations are propagated to the Oracle database, the commit is first attempted in the Oracle database.

- If an error occurs when applying the operations on the tables in the Oracle database, then all operations are rolled back on the tables on the Oracle database. If the commit fails in the Oracle database, the commit is not attempted in the TimesTen database and the application must roll back the TimesTen transaction. If the user tries to execute another statement, an error displays informing them of the need for a rollback. As a result, the Oracle database never misses updates committed in TimesTen.

2. If the commit succeeds in the Oracle database, the commit is attempted in the TimesTen database.

- If the transaction successfully commits on the Oracle database, the user's transaction is committed on TimesTen (indicated by the commit log record in the transaction log) and notifies the application. If the application ends abruptly before TimesTen informs it of the success of the local commit, TimesTen is still able to finalize the transaction commit on TimesTen based on what is saved in the transaction log.

- If the transaction successfully commits on the Oracle database and a failure occurs before returning the status of the commit on TimesTen, then no record of the successful commit is written into the transaction log and the transaction is rolled back.

- If the commit fails in TimesTen, an error message is returned from TimesTen indicating the cause of the failure. You then need to manually resynchronize the cache tables with the Oracle Database tables.

Note:
See "Synchronous writethrough (SWT) cache group" for information on how to resynchronize the cache tables with the Oracle Database tables.

You can disable propagation of committed updates on the TimesTen cached tables to the Oracle database with the ttCachePropagateFlagSet built-in procedure. This built-in procedure can enable or disable automatic propagation so that committed updates on a cache table on TimesTen for the current transaction are never propagated to the cached Oracle Database table. You can then re-enable propagation for DML statements by resetting the flag to one with the ttCachePropagateFlagSet built-in procedure. After the flag is set back to one, propagation of committed updates to the Oracle database resumes. The propagation flag automatically resets to one after the transaction is committed or rolled back. See "ttCachePropagateFlagSet" in the Oracle TimesTen In-Memory Database Reference for more details.

Example 4-9 demonstrates the use of the PROPAGATE cache table attribute in the oratt.active_customer cache table.

Restrictions for the PROPAGATE cache attribute

The following restrictions apply when using the PROPAGATE cache table attribute:

- If the cache group uses the AUTOREFRESH cache group attribute, the PROPAGATE cache table attribute must be specified on all or none of its cache tables.
See "AUTOREFRESH cache group attribute" for more information about using the AUTOREFRESH cache group attribute.

- If the cache group uses the AUTOREFRESH cache group attribute, the NOT PROPAGATE cache table attribute cannot be explicitly specified on any of its cache tables.

- You cannot use both the PROPAGATE and READONLY cache table attributes on the same cache table.
See "READONLY cache table attribute" for more information about using the READONLY cache table attribute.

- A FLUSH CACHE GROUP statement cannot be issued on the cache group unless one or more of its cache tables use neither the PROPAGATE nor the READONLY cache table attribute.
See "Flushing a user managed cache group" for more information about the FLUSH CACHE GROUP statement.

- After the PROPAGATE cache table attribute has been specified on a cache table, you cannot change this attribute unless you drop the cache group and re-create it.

- The PROPAGATE cache table attribute cannot be used when caching Oracle Database materialized views.

- TimesTen does not perform a conflict check to prevent a propagate operation from overwriting data that was updated directly on a cached Oracle Database table. Therefore, updates should only be performed directly on the TimesTen cache tables or the cached Oracle Database tables, but not both.

Examples of user managed cache groups

The following are the definitions of the Oracle Database tables that are to be cached in the user managed cache groups that are defined in Example 4-9 and Example 4-10. The Oracle Database tables are owned by the schema user oratt. The oratt user must be granted the CREATE SESSION and RESOURCE privileges before it can create tables.

CREATE TABLE active_customer
(custid NUMBER(6) NOT NULL PRIMARY KEY,
name   VARCHAR2(50),
addr   VARCHAR2(100),
zip    VARCHAR2(12),
region VARCHAR2(12) DEFAULT 'Unknown');

CREATE TABLE ordertab
(orderid NUMBER(10) NOT NULL PRIMARY KEY,
custid  NUMBER(6) NOT NULL);

CREATE TABLE cust_interests
(custid   NUMBER(6) NOT NULL,
interest VARCHAR2(10) NOT NULL,
PRIMARY KEY (custid, interest));

CREATE TABLE orderdetails
(orderid  NUMBER(10) NOT NULL,
itemid   NUMBER(8) NOT NULL,
quantity NUMBER(4) NOT NULL,
PRIMARY KEY (orderid, itemid));

Use the CREATE USERMANAGED CACHE GROUP statement to create a user managed cache group.

Example 4-9 Creating a single-table user managed cache group

The following statement creates a user managed cache group update_anywhere_customers that caches the oratt.active_customer table as shown in Figure 4-8:

CREATE USERMANAGED CACHE GROUP update_anywhere_customers
AUTOREFRESH MODE INCREMENTAL INTERVAL 30 SECONDS
FROM oratt.active_customer
(custid NUMBER(6) NOT NULL,
name   VARCHAR2(50),
addr   VARCHAR2(100),
zip    VARCHAR2(12),
PRIMARY KEY(custid),
PROPAGATE);

Figure 4-8 Single-table user managed cache group

In this example, all columns except region from the oratt.active_customer table are cached in TimesTen. Since this is defined with the PROPAGATE cache table attribute, updates committed on the oratt.active_customer cache table on TimesTen are transmitted to the oratt.active_customer cached Oracle Database table. Since the user managed cache table is also defined with the AUTOREFRESH cache attribute, any committed updates on the oratt.active_customer Oracle Database table are transmitted to the update_anywhere_customers cached table.

The companion Oracle Database user of the TimesTen cache manager user must be granted the SELECT privilege on the oratt.active_customer table in order for the cache manager user to create a user managed cache group that caches this table, and for autorefresh operations to occur from the cached Oracle Database table to the TimesTen cache table. The companion Oracle Database user must also be granted the INSERT, UPDATE and DELETE privileges on the oratt.active_customer table for synchronous writethrough operations to occur from the TimesTen cache table to the cached Oracle Database table.

In this example, the AUTOREFRESH cache group attribute specifies that committed updates on the oratt.active_customer cached Oracle Database table are automatically refreshed to the TimesTen oratt.active_customer cache table every 30 seconds.

If you manually created the Oracle Database objects used to enforce the predefined behaviors of a user managed cache group that uses the AUTOREFRESH MODE INCREMENTAL cache group attribute as described in "Manually create Oracle Database objects used to manage data caching", you need to set the autorefresh state to OFF when creating the cache group.

Then you need to run the ttIsql utility's cachesqlget command to generate a SQL*Plus script used to create a log table and a trigger in the Oracle database for each Oracle Database table that is cached in the user managed cache group.

See "Manually creating Oracle Database objects for autorefresh cache groups" for more information.

Example 4-10 Creating a multiple-table user managed cache group

The following statement creates a user managed cache group western_customers that caches the oratt.active_customer, oratt.ordertab, oratt.cust_interests, and oratt.orderdetails tables as shown in Figure 4-9:

CREATE USERMANAGED CACHE GROUP western_customers
FROM oratt.active_customer
(custid NUMBER(6) NOT NULL,
name   VARCHAR2(50),
addr   VARCHAR2(100),
zip    VARCHAR2(12),
region VARCHAR2(12),
PRIMARY KEY(custid),
PROPAGATE)
WHERE (oratt.active_customer.region = 'West'),
oratt.ordertab
(orderid NUMBER(10) NOT NULL,
custid  NUMBER(6) NOT NULL,
PRIMARY KEY(orderid),
FOREIGN KEY(custid) REFERENCES oratt.active_customer(custid),
PROPAGATE),
oratt.cust_interests
(custid   NUMBER(6) NOT NULL,
interest VARCHAR2(10) NOT NULL,
PRIMARY KEY(custid, interest),
FOREIGN KEY(custid) REFERENCES oratt.active_customer(custid),
READONLY),
oratt.orderdetails
(orderid  NUMBER(10) NOT NULL,
itemid   NUMBER(8) NOT NULL,
quantity NUMBER(4) NOT NULL,
PRIMARY KEY(orderid, itemid),
FOREIGN KEY(orderid) REFERENCES oratt.ordertab(orderid))
WHERE (oratt.orderdetails.quantity >= 5);

Figure 4-9 Multiple-table user managed cache group

Only customers in the West region who ordered at least 5 of the same item are cached.

The companion Oracle Database user of the TimesTen cache manager user must be granted the SELECT privilege on the oratt.active_customer, oratt.ordertab, oratt.cust_interests, and oratt.orderdetails tables in order for the cache manager user to create a user managed cache group that caches all of these tables. The companion Oracle Database user must also be granted the INSERT, UPDATE and DELETE privileges on the oratt.active_customer and oratt.ordertab tables for synchronous writethrough operations to occur from these TimesTen cache tables to the cached Oracle Database tables.

Each cache table in the western_customers cache group contains a primary key. Each child table references a parent table with a foreign key constraint. The oratt.active_customer root table and the oratt.orderdetails child table each contain a WHERE clause to restrict the rows to be cached. The oratt.active_customer root table and the oratt.ordertab child table both use the PROPAGATE cache table attribute so that committed updates on these cache tables are automatically propagated to the cached Oracle Database tables. The oratt.cust_interests child table uses the READONLY cache table attribute so that it cannot be updated directly.

AUTOREFRESH cache group attribute

The AUTOREFRESH cache group attribute can be specified when creating a read-only cache group or a user managed cache group using a CREATE CACHE GROUP statement. AUTOREFRESH specifies that committed updates on cached Oracle Database tables are automatically refreshed to the TimesTen cache tables. Autorefresh is defined by default on read-only cache groups.

The following are the default settings of the autorefresh attributes:

- The autorefresh mode is incremental.

- The autorefresh interval is 5 minutes.

- The autorefresh state is PAUSED.

TimesTen supports two autorefresh modes:

- INCREMENTAL: Committed updates on cached Oracle Database tables are automatically refreshed to the TimesTen cache tables based on the cache group's autorefresh interval. Incremental autorefresh mode uses Oracle Database objects to track committed updates on cached Oracle Database tables. See "Managing a caching environment with Oracle Database objects" for information on these objects.

- FULL: All cache tables are automatically refreshed, based on the cache group's autorefresh interval, by unloading all their rows and then reloading from the cached Oracle Database tables.

Incremental autorefresh mode incurs some overhead to refresh the cache group for each committed update on the cached Oracle Database tables. There is no overhead when using full autorefresh mode.

When using incremental autorefresh mode, committed updates on cached Oracle Database tables are tracked in change log tables in the Oracle database. Under certain circumstances, it is possible for some change log records to be deleted from the change log table before they are automatically refreshed to the TimesTen cache tables. If this occurs, TimesTen initiates a full automatic refresh on the cache group. See "Monitoring the cache administration user's tablespace" for information on how to configure an action to take when the tablespace that the change log tables reside in becomes full.

The change log table on the Oracle database does not have column-level resolution because of performance reasons. Thus the autorefresh operation updates all of the columns in a row. XLA reports that all of the columns in the row have changed even if the data did not actually change in each column.

The autorefresh interval determines how often autorefresh operations occur in minutes, seconds or milliseconds. Cache groups with the same autorefresh interval are refreshed within the same transaction. You can use the ttCacheAutorefresh built-in procedure to initiate an immediate autorefresh operation. For more information, see "ttCacheAutorefresh" in Oracle TimesTen In-Memory Database Reference.

The autorefresh state can be set to ON, PAUSED or OFF. Autorefresh operations are scheduled by TimesTen when the cache group's autorefresh state is ON.

When the cache group's autorefresh state is OFF, committed updates on the cached Oracle Database tables are not tracked.

When the cache group's autorefresh state is PAUSED, committed updates on the cached Oracle Database tables are tracked in the Oracle database, but are not automatically refreshed to the TimesTen cache tables until the state is changed to ON.

The following restrictions apply when using the AUTOREFRESH cache group attribute:

- A FLUSH CACHE GROUP statement cannot be issued on the cache group.
See "Flushing a user managed cache group" for more information about the FLUSH CACHE GROUP statement.

- A TRUNCATE TABLE statement issued on a cached Oracle Database table is not automatically refreshed to the TimesTen cache table. Before issuing a TRUNCATE TABLE statement on a cached Oracle Database table, use an ALTER CACHE GROUP statement to change the autorefresh state of the cache group that contains the cache table to PAUSED.
See "Altering a cache group to change the AUTOREFRESH mode, interval or state" for more information about the ALTER CACHE GROUP statement.

After issuing the TRUNCATE TABLE statement on the cached Oracle Database table, use a REFRESH CACHE GROUP statement to manually refresh the cache group.

- A LOAD CACHE GROUP statement can only be issued if the cache tables are empty, unless the cache group is dynamic.
See "Loading and refreshing a cache group" for more information about the LOAD CACHE GROUP and REFRESH CACHE GROUP statements.

See "Dynamic cache groups" for more information about dynamic cache groups.

- The autorefresh state must be PAUSED before you can issue a LOAD CACHE GROUP statement on the cache group, unless the cache group is dynamic, in which case the autorefresh state must be PAUSED or ON. The LOAD CACHE GROUP statement cannot contain a WHERE clause, unless the cache group is dynamic, in which case the WHERE clause must be followed by a COMMIT EVERY n ROWS clause.
See "Using a WHERE clause" for more information about WHERE clauses in cache group definitions and operations.

- The autorefresh state must be PAUSED before you can issue a REFRESH CACHE GROUP statement on the cache group. The REFRESH CACHE GROUP statement cannot contain a WHERE clause.

- All tables and columns referenced in WHERE clauses when creating, loading or unloading the cache group must be fully qualified. For example:
user_name.table_name and user_name.table_name.column_name

- To use the AUTOREFRESH cache group attribute in a user managed cache group, all of the cache tables must be specified with the PROPAGATE cache table attribute or all of the cache tables must be specified the READONLY cache table attribute.

- You cannot specify the AUTOREFRESH cache group attribute in a user managed cache group that contains cache tables that explicitly use the NOT PROPAGATE cache table attribute.

- The AUTOREFRESH cache table attribute cannot be used when caching Oracle Database materialized views in a user managed cache group.

- LRU aging cannot be specified on the cache group, unless the cache group is dynamic where LRU aging is defined by default.
See "LRU aging" for more information about LRU aging.

If you create a unique index on a cache group with the AUTOREFRESH cache group attribute, the index is changed to a non-unique index to avoid a constraint violation. A constraint violation could occur with a unique index because conflicting updates could occur in the same statement execution on the Oracle Database table, while each row update is executed separately in TimesTen. If the unique index exists on the Oracle Database table that is being cached, then uniqueness is enforced on the Oracle Database table and does not need to be verified again in TimesTen.

In Example 4-9, the update_anywhere_customers cache group uses the AUTOREFRESH cache group attribute.

Altering a cache group to change the AUTOREFRESH mode, interval or state

After creating an autorefresh cache group, you can use an ALTER CACHE GROUP statement to change the cache group's autorefresh mode, interval or state. You cannot use ALTER CACHE GROUP to instantiate automatic refresh for a cache group that was originally created without autorefresh defined.

If you change a cache group's autorefresh state to OFF or drop a cache group that has an autorefresh operation in progress:

- The autorefresh operation stops if the setting of the LockWait connection attribute is greater than 0. The ALTER CACHE GROUP or DROP CACHE GROUP statement preempts the autorefresh operation.

- The autorefresh operation continues if the LockWait connection attribute is set to 0. The ALTER CACHE GROUP or DROP CACHE GROUP statement is blocked until the autorefresh operation completes or the statement fails with a lock timeout error.

Example 4-11 Altering the autorefresh attributes of a cache group

The following statements change the autorefresh mode, interval and state of the customer_orders cache group:

ALTER CACHE GROUP customer_orders SET AUTOREFRESH MODE FULL;
ALTER CACHE GROUP customer_orders SET AUTOREFRESH INTERVAL 30 SECONDS;
ALTER CACHE GROUP customer_orders SET AUTOREFRESH STATE ON;

Manually creating Oracle Database objects for autorefresh cache groups

If you manually created the Oracle Database objects used to enforce the predefined behaviors of an autorefresh cache group as described in "Manually create Oracle Database objects used to manage data caching", you need to set the autorefresh state to OFF when creating the cache group.

Then you need to run the ttIsql utility's cachesqlget command with the INCREMENTAL_AUTOREFRESH option and the INSTALL flag as the cache manager user. This command generates a SQL*Plus script used to create a log table and a trigger in the Oracle database for each Oracle Database table that is cached in the autorefresh cache group. These Oracle Database objects track updates on the cached Oracle Database tables so that the updates can be automatically refreshed to the cache tables.

Next use SQL*Plus to run the script generated by the ttIsql utility's cachesqlget command as the sys user. Then use an ALTER CACHE GROUP statement to change the autorefresh state of the cache group to PAUSED.

Example 4-12 Creating a read-only cache group when Oracle Database objects were manually created

The first statement creates a read-only cache group customer_orders with the autorefresh state set to OFF. The SQL*Plus script generated by the ttIsql utility's cachesqlget command is saved to the /tmp/obj.sql file. The last statement changes the autorefresh state of the cache group to PAUSED.

CREATE READONLY CACHE GROUP customer_orders
AUTOREFRESH STATE OFF
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num)),
oratt.orders
(ord_num      NUMBER(10) NOT NULL,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL,
PRIMARY KEY(ord_num),
FOREIGN KEY(cust_num) REFERENCES oratt.customer(cust_num));

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> cachesqlget INCREMENTAL_AUTOREFRESH customer_orders INSTALL /tmp/obj.sql;
Command> exit

% sqlplus sys as sysdba
Enter password: password
SQL> @/tmp/obj
SQL> exit

ALTER CACHE GROUP customer_orders SET AUTOREFRESH STATE PAUSED;

Using a WHERE clause

A cache table definition in a CREATE CACHE GROUP statement can contain a WHERE clause to restrict the rows to cache in the TimesTen database for particular cache group types.

You can also specify a WHERE clause in a LOAD CACHE GROUP, UNLOAD CACHE GROUP, REFRESH CACHE GROUP or FLUSH CACHE GROUP statement for particular cache group types. Some statements, such as LOAD CACHE GROUP and REFRESH CACHE GROUP, may result in concatenated WHERE clauses in which the WHERE clause for the cache table definition is evaluated before the WHERE clause in the LOAD CACHE GROUP or REFRESH CACHE GROUP statement.

The following restrictions apply to WHERE clauses used in cache table definitions and cache group operations:

- WHERE clauses can only be specified in the cache table definitions of a CREATE CACHE GROUP statement for read-only and user managed cache groups.

- A WHERE clause can be specified in a LOAD CACHE GROUP statement except on an explicitly loaded autorefresh cache group.
See "Loading and refreshing a cache group" for more information about the LOAD CACHE GROUP statement.

- A WHERE clause can be specified in a REFRESH CACHE GROUP statement except on an autorefresh cache group.
See "Loading and refreshing a cache group" for more information about the REFRESH CACHE GROUP statement.

- A WHERE clause can be specified in a FLUSH CACHE GROUP statement on a user managed cache group that allows committed updates on the TimesTen cache tables to be flushed to the cached Oracle Database tables.
See "Flushing a user managed cache group" for more information about the FLUSH CACHE GROUP statement.

- WHERE clauses in a CREATE CACHE GROUP statement cannot contain a subquery. Therefore, each WHERE clause cannot reference any table other than the one in its cache table definition. However, a WHERE clause in a LOAD CACHE GROUP, UNLOAD CACHE GROUP, REFRESH CACHE GROUP or FLUSH CACHE GROUP statement may contain a subquery.

- A WHERE clause in a LOAD CACHE GROUP, REFRESH CACHE GROUP or FLUSH CACHE GROUP statement can reference only the root table of the cache group, unless the WHERE clause contains a subquery.

- WHERE clauses in the cache table definitions are only enforced when the cache group is manually loaded or refreshed, or the cache tables are dynamically loaded. If a cache table is updatable, you can insert or update a row such that the WHERE clause in the cache table definition for that row is not satisfied.

- All tables and columns referenced in WHERE clauses when creating, loading, refreshing, unloading or flushing the cache group must be fully qualified. For example:
user_name.table_name and user_name.table_name.column_name

In Example 4-10, both the oratt.active_customer and oratt.orderdetails tables contain a WHERE clause.

Proper placement of WHERE clause in a CREATE CACHE GROUP statement

In a multiple-table cache group, a WHERE clause in a particular table definition should not reference any table in the cache group other than the table itself. For example, the following CREATE CACHE GROUP statements are valid:

CREATE READONLY CACHE GROUP customer_orders
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num))
WHERE (oratt.customer.cust_num < 100),
oratt.orders
(ord_num      NUMBER(10) NOT NULL,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL,
PRIMARY KEY(ord_num),
FOREIGN KEY(cust_num) REFERENCES oratt.customer(cust_num));

CREATE READONLY CACHE GROUP customer_orders
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num)),
oratt.orders
(ord_num      NUMBER(10) NOT NULL,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL,
PRIMARY KEY(ord_num),
FOREIGN KEY(cust_num) REFERENCES oratt.customer(cust_num));
WHERE (oratt.orders.cust_num < 100)

The following statement is not valid because the WHERE clause in the child table's definition references its parent table:

CREATE READONLY CACHE GROUP customer_orders
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num)),
oratt.orders
(ord_num      NUMBER(10) NOT NULL,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL,
PRIMARY KEY(ord_num),
FOREIGN KEY(cust_num) REFERENCES oratt.customer(cust_num))
WHERE (oratt.customer.cust_num < 100);

Similarly, the following statement is not valid because the WHERE clause in the parent table's definition references its child table:

CREATE READONLY CACHE GROUP customer_orders
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num))
WHERE (oratt.orders.cust_num < 100),
oratt.orders
(ord_num      NUMBER(10) NOT NULL,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL,
PRIMARY KEY(ord_num),
FOREIGN KEY(cust_num) REFERENCES oratt.customer(cust_num));

Referencing Oracle Database PL/SQL functions in a WHERE clause

A user-defined PL/SQL function in the Oracle database can be invoked indirectly in a WHERE clause within a CREATE CACHE GROUP, LOAD CACHE GROUP, or REFRESH CACHE GROUP (for dynamic cache groups only) statement. After creating the function, create a public synonym for the function. Then grant the EXECUTE privilege on the function to PUBLIC.

For example, in the Oracle database:

CREATE OR REPLACE FUNCTION get_customer_name
(c_num oratt.customer.cust_num%TYPE) RETURN VARCHAR2 IS
c_name oratt.customer.name%TYPE;
BEGIN
SELECT name INTO c_name FROM oratt.customer WHERE cust_num = c_num;
RETURN c_name;
END get_customer_name;

CREATE PUBLIC SYNONYM retname FOR get_customer_name;
GRANT EXECUTE ON get_customer_name TO PUBLIC;

Then in the TimesTen database, for example, you can create a cache group with a WHERE clause that references the Oracle Database public synonym that was created for the function:

CREATE READONLY CACHE GROUP top_customer
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num))
WHERE name = retname(100);

For cache group types that allow a WHERE clause on a LOAD CACHE GROUP or REFRESH CACHE GROUP statement, you can invoke the function indirectly by referencing the public synonym that was created for the function. For example, you can use the following LOAD CACHE GROUP statement to load the AWT cache group new_customers:

LOAD CACHE GROUP new_customers WHERE name = retname(101) COMMIT EVERY 0 ROWS;

ON DELETE CASCADE cache table attribute

The ON DELETE CASCADE cache table attribute can be specified for cache tables in any cache group type. ON DELETE CASCADE specifies that when rows containing referenced key values are deleted from a parent table, rows in child tables with dependent foreign keys are also deleted.

Example 4-13 Using the ON DELETE CASCADE cache table attribute

The following statement uses the ON DELETE CASCADE cache table attribute on the child table's foreign key definition:

CREATE READONLY CACHE GROUP customer_orders
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num)),
oratt.orders
(ord_num      NUMBER(10) NOT NULL,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL,
PRIMARY KEY(ord_num),
FOREIGN KEY(cust_num) REFERENCES oratt.customer(cust_num) ON DELETE CASCADE);

All paths from a parent table to a child table must be either "delete" paths or "do not delete" paths. There cannot be some "delete" paths and some "do not delete" paths from a parent table to a child table. Specify the ON DELETE CASCADE cache table attribute for child tables on a "delete" path.

The following restrictions apply when using the ON DELETE CASCADE cache table attribute:

- For AWT and SWT cache groups, and for TimesTen cache tables in user managed cache groups that use the PROPAGATE cache table attribute, foreign keys in cache tables that use the ON DELETE CASCADE cache table attribute must be a proper subset of the foreign keys in the cached Oracle Database tables that use the ON DELETE CASCADE attribute. ON DELETE CASCADE actions on the cached Oracle Database tables are applied to the TimesTen cache tables as individual deletes. ON DELETE CASCADE actions on the cache tables are applied to the cached Oracle Database tables as a cascaded operation.

- Matching of foreign keys between the TimesTen cache tables and the cached Oracle Database tables is enforced only when the cache group is being created. A cascade delete operation may not work if the foreign keys on the cached Oracle Database tables are altered after the cache group is created.

See the CREATE CACHE GROUP statement in Oracle TimesTen In-Memory Database SQL Reference for more information about the ON DELETE CASCADE cache table attribute.

UNIQUE HASH ON cache table attribute

The UNIQUE HASH ON cache table attribute can be specified for cache tables in any cache group type. UNIQUE HASH ON specifies that a hash index rather than a range index is created on the primary key columns of the cache table. The columns specified in the hash index must be identical to the columns in the primary key. The UNIQUE HASH ON cache table attribute is also used to specify the size of the hash index.

Example 4-14 Using the UNIQUE HASH ON cache table attribute

The following statement uses the UNIQUE HASH ON cache table attribute on the cache table's definition.

CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP new_customers
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num))
UNIQUE HASH ON (cust_num) PAGES = 100;

See the CREATE CACHE GROUP statement in Oracle TimesTen In-Memory Database SQL Reference for more information about the UNIQUE HASH ON cache table attribute.

Caching Oracle Database synonyms

You can cache a private synonym in an AWT, SWT or user managed cache group that does not use the AUTOREFRESH cache group attribute. The private synonym can reference a public or private synonym, but it must eventually reference a table because it is the table that is actually being cached.

The table that is directly or indirectly referenced by the cached synonym can be owned by a user other than the Oracle Database user with the same name as the owner of the cache group that caches the synonym. The table must reside in the same Oracle database as the synonym. The cached synonym itself must be owned by the Oracle Database user with the same name as the owner of the cache group that caches the synonym.

Caching Oracle Database LOB data

You can cache Oracle Database large object (LOB) data in TimesTen cache groups. TimesTen caches the data as follows:

- Oracle Database CLOB data is cached as TimesTen CLOB data.

- Oracle Database BLOB data is cached as TimesTen BLOB data.

- Oracle Database NCLOB data is cached as TimesTen NCLOB data.

Example 4-15 Caching Oracle Database LOB data

Create a table in the Oracle database that has LOB fields.

CREATE TABLE t (
i INT NOT NULL PRIMARY KEY
, c CLOB
, b BLOB
, nc NCLOB);

Insert values into the Oracle Database table. The values are implicitly converted to LOB data types.

INSERT INTO t VALUES (1
, RPAD('abcdefg8', 2048, 'abcdefg8')
, HEXTORAW(RPAD('123456789ABCDEF8', 4000, '123456789ABCDEF8'))
, RPAD('abcdefg8', 2048, 'abcdefg8')
);

1 row inserted.

Create a dynamic AWT cache group and start the replication agent.

CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH CACHE GROUP cg1
FROM t
(i INT NOT NULL PRIMARY KEY
, c CLOB
, b BLOB
, nc NCLOB);

CALL ttrepstart;

Load the data dynamically into the TimesTen cache group.

SELECT * FROM t WHERE i = 1;

I:    1
C:    abcdefg8abcdefg8abcdefg8...
B:    123456789ABCDEF8123456789...
NC:   abcdefg8abcdefg8abcdefg8...

1 row found.

Restrictions on caching Oracle Database LOB data

These restrictions apply to caching Oracle Database LOB data in TimesTen cache groups:

- Column size is enforced when a cache group is created. VARBINARY, VARCHAR2 and NVARCHAR2 data types have a size limit of 4 megabytes. Values that exceed the user-defined column size are truncated at run time without notification.

- Empty values in fields with CLOB and BLOB data types are initialized but not populated with data. Empty CLOB and BLOB fields are treated as follows:

- Empty LOB fields in the Oracle database are returned as NULL values.

- Empty BLOB fields are loaded into the TimesTen cache as NULL values.

- Empty VARCHAR2 and VARBINARY fields in the TimesTen cache are propagated as NULL values.

In addition, cache groups that are configured for autorefresh operations have these restrictions on caching LOB data:

- When LOB data is updated in the Oracle database by OCI functions or the DBMS_LOB PL/SQL package, the data is not automatically refreshed in the TimesTen cache group. This occurs because TimesTen caching depends on Oracle Database triggers, and Oracle Database triggers are not executed when these types of updates occur. TimesTen does not notify the user that updates have occurred without being refreshed in TimesTen. When the LOB is updated through a SQL statement, a trigger is fired and autorefresh brings in the change.

- Autorefresh operations update a complete row in the TimesTen cache. Thus, the cached LOB data may appear to be updated in TimesTen when no change has occurred in the LOB data in the Oracle database.

Implementing aging in a cache group

You can define an aging policy for a cache group that specifies the aging type, the aging attributes, and the aging state. TimesTen supports two aging types, least recently used (LRU) aging and time-based aging.

LRU aging deletes the least recently used or referenced data based on a specified database usage range. Time-based aging deletes data based on a specified data lifetime and frequency of the aging process. You can use both LRU and time-based aging in the same TimesTen database, but you can define only one aging policy for a particular cache group.

An aging policy is specified in the cache table definition of the root table in a CREATE CACHE GROUP statement and applies to all cache tables in the cache group because aging is performed at the cache instance level. When rows are deleted from the cache tables by aging out, the rows in the cached Oracle Database table are not deleted.

You can add an aging policy to a cache group by using an ALTER TABLE statement on the root table. You can change the aging policy of a cache group by using ALTER TABLE statements on the root table to drop the existing aging policy and then add a new aging policy.

This section describes cache group definitions that contain an aging policy. The topics include:

- LRU aging

- Time-based aging

- Manually scheduling an aging process

- Configuring a sliding window

LRU aging

LRU aging enables you to maintain the amount of memory used in a TimesTen database within a specified threshold by deleting the least recently used data. LRU aging can be defined for all cache group types except explicitly loaded autorefresh cache groups. LRU aging is defined by default on dynamic cache groups.

Define an LRU aging policy for a cache group by using the AGING LRU clause in the cache table definition of the CREATE CACHE GROUP statement. Aging occurs automatically if the aging state is set to its default of ON.

Example 4-16 Defining an LRU aging policy on a cache group

The following statement defines an LRU aging policy on the AWT cache group new_customers:

CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP new_customers
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num))
AGING LRU ON;

Use the ttAgingLRUConfig built-in procedure to set the LRU aging attributes as a user with the ADMIN privilege. The attribute settings apply to all tables in the TimesTen database that have an LRU aging policy defined and an aging state of ON.

The following are the LRU aging attributes:

- LowUsageThreshold: The TimesTen database's space usage (the ratio of the permanent region's in-use size over the region's allocated size) at or below which LRU aging is deactivated. The default low usage threshold is .8 (80 percent).

- HighUsageThreshold: The TimesTen database's space usage above which LRU aging is activated. The default high usage threshold is .9 (90 percent).

- AgingCycle: The frequency in which aging occurs, in minutes. The default aging cycle is 1 minute.

Example 4-17 Setting the LRU aging attributes

The following built-in procedure call specifies that the aging process checks every 5 minutes to see if the TimesTen database's permanent region space usage is above 95 percent. If it is, the least recently used data is automatically aged out or deleted until the space usage is at or below 75 percent.

Command> CALL ttAgingLRUConfig(.75, .95, 5);

If you set a new value for AgingCycle after an LRU aging policy has been defined on a cache group, the next time aging occurs is based on the current system time and the new aging cycle. For example, if the original aging cycle was 15 minutes and LRU aging occurred 10 minutes ago, aging is expected to occur again in 5 minutes. However, if you change the aging cycle to 30 minutes, aging next occurs 30 minutes from the time you call the ttAgingLRUConfig built-in procedure with the new aging cycle setting.

If a row has been accessed or referenced since the last aging cycle, it is not eligible for LRU aging in the current aging cycle. A row is considered to be accessed or referenced if at least one of the following is true:

- The row is used to build the result set of a SELECT or an INSERT ... SELECT statement.

- The row has been marked to be updated or deleted in a pending transaction.

In a multiple-table cache group, if a row in a child table has been accessed or referenced since the last aging cycle, then neither the related row in the parent table nor the row in the child table is eligible for LRU aging in the current aging cycle.

The ALTER TABLE statement can be used to perform the following tasks associated with changing or defining an LRU aging policy on a cache group:

- Change the aging state of a cache group by specifying the root table and using the SET AGING clause.

- Add an LRU aging policy to a cache group that has no aging policy defined by specifying the root table and using the ADD AGING LRU clause.

- Drop the LRU aging policy on a cache group by specifying the root table and using the DROP AGING clause.

To change the aging policy of a cache group from LRU to time-based, use an ALTER TABLE statement on the root table with the DROP AGING clause to drop the LRU aging policy. Then use an ALTER TABLE statement on the root table with the ADD AGING USE clause to add a time-based aging policy.

You must stop the cache agent before you add, alter or drop an aging policy on an autorefresh cache group.

Time-based aging

Time-based aging deletes data from a cache group based on the aging policy's specified data lifetime and frequency. Time-based aging can be defined for all cache group types.

Define a time-based aging policy for a cache group by using the AGING USE clause in the cache table definition of the CREATE CACHE GROUP statement. Aging occurs automatically if the aging state is set to its default of ON.

The definitions of the Oracle Database tables that are to be cached in the AWT cache group defined in Example 4-19 are defined in Example 4-18. The Oracle Database tables are owned by the schema user oratt. The oratt user must be granted the CREATE SESSION and RESOURCE privileges before it can create tables.

Example 4-18 Oracle Database table definitions

CREATE TABLE orders
(ord_num      NUMBER(10) NOT NULL PRIMARY KEY,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL);

CREATE TABLE order_item
(orditem_id NUMBER(12) NOT NULL PRIMARY KEY,
ord_num    NUMBER(10),
prod_num   VARCHAR2(6),
quantity   NUMBER(3));

The companion Oracle Database user of the TimesTen cache manager user must be granted the SELECT privilege on the oratt.orders and oratt.order_item tables in order for the cache manager user to create an AWT cache group that caches these tables. The cache administration user must be granted the INSERT, UPDATE and DELETE Oracle Database privileges for the oratt.orders and oratt.order_item tables for asynchronous writethrough operations to be applied on the Oracle Database.

Example 4-19 Defining a time-based aging policy on a cache group

The following statement defines a time-based aging policy on the AWT cache group ordered_items:

CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP ordered_items
FROM oratt.orders
(ord_num      NUMBER(10) NOT NULL,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL,
PRIMARY KEY(ord_num))
AGING USE when_placed LIFETIME 45 DAYS CYCLE 60 MINUTES ON,
oratt.order_item
(orditem_id NUMBER(12) NOT NULL,
ord_num    NUMBER(10),
prod_num   VARCHAR2(6),
quantity   NUMBER(3),
PRIMARY KEY(orditem_id),
FOREIGN KEY(ord_num) REFERENCES oratt.orders(ord_num));

Cache instances that are greater than 45 days old based on the difference between the current system timestamp and the timestamp in the when_placed column of the oratt.orders table are candidates for aging. The aging process checks every 60 minutes to see if there are cache instances that can be automatically aged out or deleted from the cache tables.

The AGING USE clause requires the name of a non-nullable TIMESTAMP or DATE column used for time-based aging. We refer to this column as the timestamp column.

For each row, the value in the timestamp column stores the date and time when the row was most recently inserted or updated. The values in the timestamp column is maintained by your application. If the value of this column is unknown for particular rows and you do not want those rows to be aged out of the table, define the timestamp column with a large default value.

You can create an index on the timestamp column to optimize performance of the aging process.

You cannot add a column to an existing table and then use that column as the timestamp column because added columns cannot be defined as non-nullable. You cannot drop the timestamp column from a table that has a time-based aging policy defined.

Specify the lifetime in days, hours, minutes or seconds after the LIFETIME keyword in the AGING USE clause.

The value in the timestamp column is subtracted from the current system timestamp. The result is then truncated to the specified lifetime unit (day, hour, minute, second) and compared with the specified lifetime value. If the result is greater than the lifetime value, the row is a candidate for aging.

After the CYCLE keyword, specify the frequency in which aging occurs in days, hours, minutes or seconds. The default aging cycle is 5 minutes. If you specify an aging cycle of 0, aging is continuous.

The ALTER TABLE statement can be used to perform the following tasks associated with changing or defining a time-based aging policy on a cache group:

- Change the aging state of a cache group by specifying the root table and using the SET AGING clause.

- Change the lifetime by specifying the root table and using the SET AGING LIFETIME clause.

- Change the aging cycle by specifying the root table and using the SET AGING CYCLE clause.

- Add a time-based aging policy to a cache group that has no aging policy defined by specifying the root table and using the ADD AGING USE clause.

- Drop the time-based aging policy on a cache group by specifying the root table and using the DROP AGING clause.

To change the aging policy of a cache group from time-based to LRU, use an ALTER TABLE statement on the root table with the DROP AGING clause to drop the time-based aging policy. Then use an ALTER TABLE statement on the root table with the ADD AGING LRU clause to add an LRU aging policy.

You must stop the cache agent before you add, alter or drop an aging policy on an autorefresh cache group.

Manually scheduling an aging process

Use the ttAgingScheduleNow built-in procedure to manually start a one-time aging process on a specified table or on all tables that have an aging policy defined. The aging process starts as soon as you call the built-in procedure unless there is already an aging process in progress. Otherwise the manually started aging process begins when the aging process that is in progress has completed. After the manually started aging process has completed, the start of the table's next aging cycle is set to the time when ttAgingScheduleNow was called if the table's aging state is ON.

Example 4-20 Starting a one-time aging process

The following built-in procedure call starts a one-time aging process on the oratt.orders table based on the time ttAgingScheduleNow is called:

Command> CALL ttAgingScheduleNow('oratt.orders');

Rows in the oratt.orders root table that are candidates for aging are deleted as well as related rows in the oratt.order_item child table.

When you call the ttAgingScheduleNow built-in procedure, the aging process starts regardless of whether the table's aging state is ON or OFF. If you want to start an aging process on a particular cache group, specify the name of the cache group's root table when you call the built-in procedure. If the ttAgingScheduleNow built-in procedure is called with no parameters, it starts an aging process and then resets the start of the next aging cycle on all tables in the TimesTen database that have an aging policy defined.

Calling the ttAgingScheduleNow built-in procedure does not change the aging state of any table. If a table's aging state is OFF when you call the built-in procedure, the aging process starts, but it is not scheduled to run again after the process has completed. To continue aging a table whose aging state is OFF, you must call ttAgingScheduleNow again or change the table's aging state to ON.

To manually control aging on a cache group, disable aging on the root table by using an ALTER TABLE statement with the SET AGING OFF clause. Then call ttAgingScheduleNow to start an aging process on the cache group.

Configuring a sliding window

You can use time-based aging to implement a sliding window for a cache group. In a sliding window configuration, new rows are inserted into and old rows are deleted from the cache tables on a regular schedule so that the tables contain only the data that satisfies a specific time interval.

You can configure a sliding window for a cache group by using incremental autorefresh mode and defining a time-based aging policy. The autorefresh operation checks the timestamp of the rows in the cached Oracle Database tables to determine whether new data should be refreshed into the TimesTen cache tables. The system time and the time zone must be identical on the Oracle Database and TimesTen systems.

If the cache group does not use incremental autorefresh mode, you can configure a sliding window by using a LOAD CACHE GROUP, REFRESH CACHE GROUP, or INSERT statement, or a dynamic load operation to bring new data into the cache tables.

Example 4-21 Defining a cache group with sliding window properties

The following statement configures a sliding window on the read-only cache group recent_shipped_orders:

CREATE READONLY CACHE GROUP recent_shipped_orders
AUTOREFRESH MODE INCREMENTAL INTERVAL 1440 MINUTES STATE ON
FROM oratt.orders
(ord_num      NUMBER(10) NOT NULL,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL,
PRIMARY KEY(ord_num))
AGING USE when_shipped LIFETIME 30 DAYS CYCLE 24 HOURS ON;

New data in the oratt.orders cached Oracle Database table are automatically refreshed into the oratt.orders TimesTen cache table every 1440 minutes. Cache instances that are greater than 30 days old based on the difference between the current system timestamp and the timestamp in the when_shipped column are candidates for aging. The aging process checks every 24 hours to see if there are cache instances that can be aged out of the cache tables. Therefore, this cache group stores orders that have been shipped within the last 30 days.

The autorefresh interval and the lifetime used for aging determine the duration that particular rows remain in the cache tables. It is possible for data to be aged out of the cache tables before it has been in the cache tables for its lifetime. For example, for a read-only cache group if the autorefresh interval is 3 days and the lifetime is 30 days, data that is already 3 days old when it is refreshed into the cache tables is deleted after 27 days because aging is based on the timestamp stored in the rows of the cached Oracle Database tables that gets loaded into the TimesTen cache tables, not when the data is refreshed into the cache tables.

Dynamic cache groups

The data in a dynamic cache group is loaded on demand. For example, a call center application may not want to preload all of its customers' information into TimesTen as it may be very large. Instead it can use a dynamic cache group so that a specific customer's information is loaded only when needed such as when the customer calls or logs onto the system.

Any system managed cache group type (read-only, AWT, SWT) can be defined as a dynamic cache group. A user managed cache group can be defined as a dynamic cache group unless it uses both the AUTOREFRESH cache group attribute and the PROPAGATE cache table attribute.

Use the CREATE DYNAMIC CACHE GROUP statement to create a dynamic cache group.

Example 4-22 Dynamic read-only cache group

This following statement creates a dynamic read-only cache group online_customers that caches the oratt.customer table:

CREATE DYNAMIC READONLY CACHE GROUP online_customers
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num));

With an explicitly loaded cache group, data is initially loaded into the cache tables from the cached Oracle Database tables using a LOAD CACHE GROUP statement. With a dynamic cache group, data may also be loaded into the cache tables using a LOAD CACHE GROUP statement. However, with a dynamic cache group, data is typically loaded automatically when its cache tables are referenced by a SELECT, INSERT, or UPDATE statement and the data is not found in the tables resulting in a cache miss. See "Dynamically loading a cache instance" for more information.

With both explicitly loaded and dynamic cache groups, a LOAD CACHE GROUP statement loads into their cache tables qualified data that exists in the cached Oracle Database tables but not in the TimesTen cache tables. However, if a row exists in a cache table but a newer version exists in the cached Oracle Database table, a LOAD CACHE GROUP statement does not load that row into the cache table even if it satisfies the predicate of the statement.

By contrast, a REFRESH CACHE GROUP statement reloads qualifying rows that exists in the cache tables, effectively refreshing the content of the cache. For an explicitly loaded cache group, the rows that are refreshed are all the rows that satisfy the predicate of the REFRESH CACHE GROUP statement. However, for a dynamic cache group, the rows that are refreshed are the ones that satisfy the predicate and already exist in the cache tables. In other words, rows that end up being refreshed are the ones that have been updated or deleted in the cached Oracle Database table, but not the ones that have been inserted. Therefore, a refresh operation processes only the rows that are already in the cache tables. No new rows are loaded into the cache tables of a dynamic cache group as a result of a refresh.

The data in the cache instance of a dynamic read-only cache group is consistent with the data in the corresponding rows of the Oracle Database tables. At any instant in time, the data in a cache instance of an explicitly loaded cache group is consistent with the data in the corresponding rows of the Oracle Database tables, taking into consideration the state and the interval settings for autorefresh.

The data in a dynamic cache group is subject to aging as LRU aging is defined by default. You can use the ttAgingLRUConfig built-in procedure to override the default or current LRU aging attribute settings for the aging cycle and TimesTen database space usage thresholds. Alternatively, you can define time-based aging on a dynamic cache group to override LRU aging. Rows in a dynamic AWT cache group must be propagated to the Oracle database before they become candidates for aging.

Global cache groups

An Oracle Database table cannot be cached in more than one cache group within the same TimesTen database. However, the table can be cached in separate cache groups in different TimesTen databases. If the table is cached in separate AWT cache groups and the same cache instance is updated simultaneously on multiple TimesTen databases, there is no guarantee as to the order in which the updates are propagated to the cached Oracle Database table. Also, the contents of the updated cache table are inconsistent between the TimesTen databases.

A TimesTen cache grid prevents this problem by providing users with Oracle databases a means to horizontally scale out global cache groups across multiple systems with read/write data consistency across the TimesTen databases. A cache grid is a set of TimesTen databases that collectively manage the application data cached in global cache groups.

Tables that are cached in separate cache groups within different TimesTen databases must be cached in global cache groups in order for the cache grid to manage consistency of the cache instances across the grid members when updates are committed on the cache tables of the global cache group. In a cache grid, only one copy of a cache instance is allowed to be present in the entire grid at any moment in time. Each cache instance in a global cache group is owned by the grid member where it is currently located. Only the cache grid member that owns the cache instance has the right to update the data. The TimesTen cache grid tracks the ownership for each cache instance, so that it can quickly locate the grid member where each cache instance is currently located and ensure that the same cache instance is not concurrently present in multiple grid members. However, another grid member can obtain ownership of the cache instance from the current owner.

Global cache groups can be defined as dynamic AWT cache groups or as explicitly loaded AWT cache groups.

This section includes the following topics:

- Dynamic global cache groups

- Explicitly loaded global cache groups

- Start the replication agent

- Attach a TimesTen database to a cache grid

Dynamic global cache groups

The following statement is the definition of the Oracle Database table that are to be cached in the dynamic AWT global cache group that is created in Example 4-23. The Oracle Database table is owned by the schema user oratt. The oratt user must be granted the CREATE SESSION and RESOURCE privileges before it can create tables.

CREATE TABLE subscriber
(subscriberid       NUMBER(10) NOT NULL PRIMARY KEY,
name               VARCHAR2(100) NOT NULL,
minutes_balance    NUMBER(5) NOT NULL,
last_call_duration NUMBER(4) NOT NULL);

The Oracle Database user with the same name as the TimesTen cache manager user must be granted the SELECT privilege on the oratt.subscriber table so that the cache manager user can create an AWT cache group that caches this table. The cache administration user must be granted the INSERT, UPDATE and DELETE Oracle Database privileges for the oratt.subscriber table for asynchronous writethrough operations to be applied to the Oracle Database.

Use the CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH GLOBAL CACHE GROUP statement to create a dynamic AWT global cache group.

Example 4-23 Dynamic global cache group

The following statement creates a dynamic AWT global cache group subscriber_accounts that caches the oratt.subscriber table:

CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH GLOBAL CACHE GROUP subscriber_accounts
FROM oratt.subscriber
(subscriberid       NUMBER(10) NOT NULL PRIMARY KEY,
name               VARCHAR2(100) NOT NULL,
minutes_balance    NUMBER(5) NOT NULL,
last_call_duration NUMBER(4) NOT NULL);

When a subscriber to a prepaid telephone account makes a call, the cache instance that contains the subscriber's account balance is loaded into the oratt.subscriber cache table of the subscriber_accounts global cache group within one of the cache grid members. The query for the account balance information first searches the grid member on which the query is issued. If the cache tables on the local grid member do not contain data that satisfies a query, then the cache instance is transferred from other grid members to the local grid member in a grid data transfer operation. If the grid does not contain the cache instance that satisfies the query, data is loaded from the Oracle Database tables. When data is loaded into the local grid member from the Oracle Database tables, this operation is called a dynamic load. The grid member that the cache instance is loaded into becomes the owner of the cache instance. Other grid members cannot access the cache instance until the owner has updated the balance of minutes and the duration of the last call, and the committed update has been propagated to the cached Oracle Database table.

To ensure consistency among the grid members, an Oracle Database table that is cached in a global cache group in a TimesTen database should not also be cached in a local cache group in another TimesTen database within the same cache grid. In addition, the Oracle Database table should not be cached in a global cache group in another TimesTen database within a different cache grid.

For cache tables in a dynamic global cache group, a particular cache instance can be read or updated by only one grid member at a time. This grid member is referred to as the owner of the cache instance. When the owner no longer has a pending transaction on any row of the cache instance, another grid member can take ownership by reading or updating that instance. The owner relinquishes ownership of a cache instance when the instance has been deleted from that grid member as a result of:

- Aging

- A DELETE statement issued on the cache table

- An UNLOAD CACHE GROUP statement issued on the cache group

- A request from another grid member to take ownership of that instance

The owner relinquishes ownership of all its cache instances if that grid member detaches from its cache grid.

Read data consistency between nodes of a cache grid is guaranteed only when using serializable isolation level on the node where cache instances are being read. When using the default read committed isolation level, a connection on a grid node that is reading a cache instance may see a data value that has been subsequently updated to a new value by another connection in the same or a different node.

The cache tables in a dynamic global cache group can be populated using any of these operations:

- Dynamic load operation

- Grid data transfer operation

- INSERT statement on the cache tables (but not an INSERT INTO ... SELECT FROM statement)

- LOAD CACHE GROUP ... COMMIT EVERY n ROWS statement (can only be used if all the other grid members do not own any of the cache instances to be loaded)

See "Dynamically loading a cache instance" for information about a dynamic load operation.

A grid member can take ownership of a cache instance that is currently owned by another grid member by using any of the following operations:

- Grid data transfer operation

- Dynamic load operation

- LOAD CACHE GROUP ... WITH ID statement

A REFRESH CACHE GROUP statement can be issued on a dynamic global cache group only if it contains a WITH ID clause.

You can set the CacheGridMsgWait connection attribute to the maximum number of seconds that a grid member waits for the owner to relinquish the instance. The owner cannot relinquish ownership of a cache instance if it has a pending transaction on any row of the instance. The default maximum wait time is 60 seconds.

An INSERT statement issued on a cache table in a dynamic global cache group fails if the unique key value in the inserted row already exists in the cached Oracle Database table.

When using a LOAD CACHE GROUP ... COMMIT EVERY n ROWS statement, if any of the cache instances to be loaded within a transaction are owned by another grid member, an error is returned. The transaction is then rolled back and no cache instances are loaded within the failed transaction.

To prevent conflicts that can occur if you update the same row in a TimesTen cache table and the cached Oracle Database table concurrently, update only the cache table. The cached Oracle Database table should not be updated directly.

A TimesTen database that is a member of a cache grid can contain local and global cache groups. Only cache tables in global cache groups are guaranteed to be consistent among the grid members.

Explicitly loaded global cache groups

Cache instances in an explicitly loaded global cache group are initially loaded from the Oracle database. You can reload the cache instances by issuing another LOAD CACHE GROUP statement or reload a single cache instance with the REFRESH CACHE GROUP...WITH ID statement.

If the cache tables on the local grid member do not contain data that satisfies a query, then the cache instance is transferred from other grid members to the local grid member in a grid data transfer operation. If the grid does not contain the cache instance that satisfies the query, data is not loaded from the Oracle Database tables. The query returns no results.

Use the CREATE ASYNCHRONOUS WRITETHROUGH GLOBAL CACHE GROUP statement to create an explicitly loaded global cache group. Note that this SQL statement is the same as the SQL statement that creates a dynamic global cache group except that the DYNAMIC keyword is omitted.

Example 4-24 Creating an explicitly loaded global cache group

The following statement creates an explicitly loaded AWT global cache group subscriber_accounts that caches the oratt.subscriber table:

CREATE ASYNCHRONOUS WRITETHROUGH GLOBAL CACHE GROUP subscriber_accounts
FROM oratt.subscriber
(subscriberid       NUMBER(10) NOT NULL PRIMARY KEY,
name               VARCHAR2(100) NOT NULL,
minutes_balance    NUMBER(5) NOT NULL,
last_call_duration NUMBER(4) NOT NULL);

The cache tables in an explicitly loaded global cache group can be populated at any time using any of these operations:

- Grid data transfer operation

- INSERT statement on the cache tables (but not an INSERT INTO ... SELECT FROM statement)

- LOAD CACHE GROUP statement. The statement can be used only if other grid members do not own any of the cache instances to be loaded into the local grid member.

- REFRESH CACHE GROUP ... WITH ID statement

Aging is disabled by default on an explicitly loaded global cache group.

Set the CacheGridMsgWait connection attribute to the maximum number of seconds that a grid member waits for the owner to relinquish the instance. The owner cannot relinquish ownership of a cache instance if it has a pending transaction on any row of the instance. The default maximum wait time is 60 seconds.

If a query that specifies a primary key or foreign key is issued on a cache table where there is no row that satisfies the query, the cache instance is not transferred to the cache table.

If a row is inserted into a child table whose parent table exists in the cache grid, the cache instance is transferred to the member with the child table. An insert into a child table whose parent is not in the cache grid fails.

Start the replication agent

After you have created a global cache group, start the replication agent on the TimesTen database as the cache manager user, if it is not already running:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> call ttRepStart;
Command> exit

Attach a TimesTen database to a cache grid

All standalone TimesTen databases, and the active and standby databases of an active standby pair that contain global cache groups must attach to the cache grid that they are associated with in order to update the cache tables of the global cache groups. Attaching the databases to the grid allow the databases to become members of the grid so that cache instances in the cache tables of the global cache groups can maintain consistency among the databases within the grid.

Example 4-25 Attaching a TimesTen database to a cache grid

Attach the first standalone database to the ttGrid cache grid that it is associated with by calling the ttGridAttach built-in procedure as the cache manager user. The node number for a standalone TimesTen database is 1. Calling the ttGridAttach built-in procedure automatically starts the cache agent on the TimesTen database if it is not already running.

In this example, alone1 is a name that uniquely identifies the grid member, sys1 is the host name of the TimesTen system where the first standalone database resides, and 5001 is the TCP/IP port for the first standalone database's cache agent process:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> call ttGridAttach(1,'alone1','sys1',5001);
Command> exit

Specify a port for the cache agent on each TimesTen database that attaches to the grid. There is no default port number. A typical grid uses the same port for each member of the grid, but different ports can be specified if desired. The port assignment is a grid member property. The only way to change the properties of a grid member after it has been attached to the grid is to destroy the grid and re-create it. Use the ttGridNodeStatus built-in procedure to determine the members of a grid and their ports.

See "Configuring a cache grid" for more information about a cache grid.

5 Cache Group Operations

The following sections describe operations that can be performed on cache groups:

- Transmitting updates between the TimesTen and Oracle databases

- Loading and refreshing a cache group

- Dynamically loading a cache instance

- Flushing a user managed cache group

- Unloading a cache group

- Setting a passthrough level

Note:
You can use SQL statements or SQL Developer to perform most of the operations in this chapter. For more information about SQL Developer, see Oracle SQL Developer Oracle TimesTen In-Memory Database Support User's Guide.

Transmitting updates between the TimesTen and Oracle databases

You can use the following SQL statements to manually transmit committed updates between the TimesTen cache tables and the cached Oracle Database tables:

SQL statement

Description

LOAD CACHE GROUP

Load cache instances that are not in the TimesTen cache tables from the cached Oracle Database tables.

REFRESH CACHE GROUP

Replace cache instances in the TimesTen cache tables with current data from the cached Oracle Database tables.

FLUSH CACHE GROUP

Propagate committed updates on the TimesTen cache tables to the cached Oracle Database tables. Only applicable for user managed cache groups.

For AWT, SWT, and user managed cache groups that use the PROPAGATE cache table attribute, committed updates on the TimesTen cache tables are automatically propagated to the cached Oracle Database tables.

See "Asynchronous writethrough (AWT) cache group" for more information about AWT cache groups.

See "Synchronous writethrough (SWT) cache group" for more information about SWT cache groups.

See "PROPAGATE cache table attribute" for more information about using the PROPAGATE cache table attribute on cache tables in a user managed cache group.

The AUTOREFRESH cache group attribute can be used in a read-only or a user managed cache group to automatically refresh committed updates on cached Oracle Database tables into the TimesTen cache tables. Automatic refresh can be defined on explicitly loaded or dynamic cache groups.

See "AUTOREFRESH cache group attribute" for more information about automatically refreshing a cache group.

Data is manually preloaded into the cache tables of explicitly loaded cache groups. For dynamic cache groups, data is loaded on demand into the cache tables. A cache instance is automatically loaded from the cached Oracle Database tables when a particular statement does not find the data in the cache tables.

See "Dynamically loading a cache instance" for more information about a dynamic load operation.

Dynamic cache groups are typically configured to automatically age out from the cache tables data that is no longer being used.

Loading and refreshing a cache group

You can manually insert or update cache instances in the TimesTen cache tables from the cached Oracle Database tables using either a LOAD CACHE GROUP or REFRESH CACHE GROUP statement. The differences between loading and refreshing a cache group are:

- LOAD CACHE GROUP only loads committed inserts on the cached Oracle Database tables into the TimesTen cache tables. New cache instances are loaded into the cache tables, but cache instances that already exist in the cache tables are not updated or deleted even if the corresponding rows in the cached Oracle Database tables have been updated or deleted. A load operation is primarily used to initially populate a cache group.

- REFRESH CACHE GROUP replaces cache instances in the TimesTen cache tables with the most current data from the cached Oracle Database tables including cache instances that are already exist in the cache tables. A refresh operation is primarily used to update the contents of a cache group with committed updates on the cached Oracle Database tables after the cache group has been initially populated.
For an explicitly loaded cache group, a refresh operation is equivalent to issuing an UNLOAD CACHE GROUP statement followed by a LOAD CACHE GROUP statement on the cache group. In effect, all committed inserts, updates and deletes on the cached Oracle Database tables are refreshed into the cache tables. New cache instances may be loaded into the cache tables. Cache instances that already exist in the cache tables are updated or deleted if the corresponding rows in the cached Oracle Database tables have been updated or deleted. See "Unloading a cache group" for more information about the UNLOAD CACHE GROUP statement.

For a dynamic cache group, a refresh operation only refreshes committed updates and deletes on the cached Oracle Database tables into the cache tables because only existing cache instances in the cache tables are refreshed. New cache instances are not loaded into the cache tables so after the refresh operation completes, the cache tables contain either the same or fewer number of cache instances. To load new cache instances into the cache tables of a dynamic cache group, use a LOAD CACHE GROUP statement or perform a dynamic load operation. See "Dynamically loading a cache instance" for more information about a dynamic load operation.

For most cache group types, you can use a WHERE clause in a LOAD CACHE GROUP or REFRESH CACHE GROUP statement to restrict the rows to be loaded or refreshed into the cache tables.

If the cache table definitions use a WHERE clause, only rows that satisfy the WHERE clause are loaded or refreshed into the cache tables even if the LOAD CACHE GROUP or REFRESH CACHE GROUP statement does not use a WHERE clause.

A REFRESH CACHE GROUP statement can be issued on a global cache group only if it contains a WITH ID clause.

If the cache group has a time-based aging policy defined, only cache instances where the timestamp in the root table's row is within the aging policy's lifetime are loaded or refreshed into the cache tables.

To prevent a load or refresh operation from processing a large number of cache instances within a single transaction, which can greatly reduce concurrency and throughput, use the COMMIT EVERY n ROWS clause to specify a commit frequency unless you are using the WITH ID clause. If you specify COMMIT EVERY 0 ROWS, the load or refresh operation is processed in a single transaction.

A LOAD CACHE GROUP or REFRESH CACHE GROUP statement that uses the COMMIT EVERY n ROWS clause must be performed in its own transaction without any other operations within the same transaction.

Example 5-1 Loading a cache group

The following statement loads new cache instances into the TimesTen cache tables in the customer_orders cache group from the cached Oracle Database tables:

LOAD CACHE GROUP customer_orders COMMIT EVERY 256 ROWS;

Example 5-2 Loading a cache group using a WHERE clause

The following statement loads into the TimesTen cache tables in the new_customers cache group from the cached Oracle Database tables, new cache instances for customers whose customer number is greater than or equal to 5000:

LOAD CACHE GROUP new_customers WHERE (oratt.customer.cust_num >= 5000)
COMMIT EVERY 256 ROWS;

Example 5-3 Refreshing a cache group

The following statement refreshes cache instances in the TimesTen cache tables within the top_products cache group from the cached Oracle Database tables:

REFRESH CACHE GROUP top_products COMMIT EVERY 256 ROWS;

Example 5-4 Refreshing a cache group using a WHERE clause

The following statement refreshes in the TimesTen cache tables within the update_anywhere_customers cache group from the cached Oracle Database tables, cache instances of customers located in zip code 60610:

REFRESH CACHE GROUP update_anywhere_customers
WHERE (oratt.customer.zip = '60610') COMMIT EVERY 256 ROWS;

For more information, see the "LOAD CACHE GROUP" and "REFRESH CACHE GROUP" statements in Oracle TimesTen In-Memory Database SQL Reference.

The rest of this section includes these topics:

- Loading and refreshing an explicitly loaded cache group with autorefresh

- Loading and refreshing a dynamic cache group with autorefresh

- Loading and refreshing a cache group using a WITH ID clause

- Initiating an immediate autorefresh

- Loading and refreshing a multiple-table cache group

- Improving the performance of loading or refreshing a large number of cache instances

- Example of manually loading and refreshing an explicitly loaded cache group

- Example of manually loading and refreshing a dynamic cache group

Loading and refreshing an explicitly loaded cache group with autorefresh

If the autorefresh state of an explicitly loaded cache group is PAUSED, the autorefresh state is changed to ON after a LOAD CACHE GROUP or REFRESH CACHE GROUP statement issued on the cache group completes.

The following restrictions apply when manually loading or refreshing an explicitly loaded cache group with autorefresh:

- A LOAD CACHE GROUP statement can only be issued if the cache tables are empty.

- The autorefresh state must be PAUSED before you can issue a LOAD CACHE GROUP statement.

- The autorefresh state must be PAUSED before you can issue a REFRESH CACHE GROUP statement.

- A LOAD CACHE GROUP statement cannot contain a WHERE clause.

- A LOAD CACHE GROUP or REFRESH CACHE GROUP statement cannot contain a WITH ID clause.

- A REFRESH CACHE GROUP statement cannot contain a WHERE clause.

- All tables and columns referenced in a WHERE clause when loading the cache group must be fully qualified. For example:
user_name.table_name and user_name.table_name.column_name

When an autorefresh operation occurs on an explicitly loaded cache group, all committed inserts, updates and deletes on the cached Oracle Database tables since the last autorefresh cycle are refreshed into the cache tables. New cache instances may be loaded into the cache tables. Cache instances that already exist in the cache tables are updated or deleted if the corresponding rows in the cached Oracle Database tables have been updated or deleted.

Loading and refreshing a dynamic cache group with autorefresh

If the autorefresh state of a dynamic cache group is PAUSED, the autorefresh state is changed to ON after any of the following events occur:

- Its cache tables are initially empty, and then a dynamic load, a LOAD CACHE GROUP or an unconditional REFRESH CACHE GROUP statement issued on the cache group completes.

- Its cache tables are not empty, and then an unconditional REFRESH CACHE GROUP statement issued on the cache group completes.

If the autorefresh state of a dynamic cache group is PAUSED, the autorefresh state remains at PAUSED after any of the following events occur:

- Its cache tables are initially empty, and then a REFRESH CACHE GROUP ... WITH ID statement issued on the cache group completes.

- Its cache tables are not empty, and then a dynamic load, a REFRESH CACHE GROUP ... WITH ID, or a LOAD CACHE GROUP statement issued on the cache group completes.

For a dynamic cache group, an autorefresh operation only refreshes committed updates and deletes on the cached Oracle Database tables since the last autorefresh cycle into the cache tables because only existing cache instances in the cache tables are refreshed. New cache instances are not loaded into the cache tables. To load new cache instances into the cache tables of a dynamic cache group, use a LOAD CACHE GROUP statement or perform a dynamic load operation. See "Dynamically loading a cache instance" for more information about a dynamic load operation.

The following restrictions apply when manually loading or refreshing a dynamic cache group with automatic refresh:

- The autorefresh state must be PAUSED or ON before you can issue a LOAD CACHE GROUP statement.

- The autorefresh state must be PAUSED before you can issue a REFRESH CACHE GROUP statement.

- A LOAD CACHE GROUP statement that contains a WHERE clause must include a COMMIT EVERY n ROWS clause after the WHERE clause.

- A REFRESH CACHE GROUP statement cannot contain a WHERE clause.

- All tables and columns referenced in a WHERE clause when loading the cache group must be fully qualified. For example:
user_name.table_name and user_name.table_name.column_name

Loading and refreshing a cache group using a WITH ID clause

The WITH ID clause of the LOAD CACHE GROUP or REFRESH CACHE GROUP statement enables you to load or refresh a cache group based on values of the primary key columns without having to use a WHERE clause. The WITH ID clause is more convenient than the equivalent WHERE clause if the primary key contains more than one column. Using the WITH ID clause allows you to load one cache instance at a time. It also enables you to roll back the transaction containing the load or refresh operation, if necessary, unlike the equivalent statement that uses a WHERE clause because using a WHERE clause also requires specifying a COMMIT EVERY n ROWS clause.

Example 5-5 Loading a cache group using a WITH ID clause

A cache group recent_orders contains a single cache table oratt.orderdetails with a primary key of (orderid, itemid). If a customer calls about an item within a particular order, the information can be obtained by loading the cache instance for the specified order number and item number.

Load the oratt.orderdetails cache table in the recent_orders cache group with the row whose value in the orderid column of the oratt.orderdetails cached Oracle Database table is 1756 and its value in the itemid column is 573:

LOAD CACHE GROUP recent_orders WITH ID (1756,573);

The following is an equivalent LOAD CACHE GROUP statement that uses a WHERE clause:

LOAD CACHE GROUP recent_orders WHERE orderid = 1756 and itemid = 573
COMMIT EVERY 256 ROWS;

A LOAD CACHE GROUP or REFRESH CACHE GROUP statement issued on an autorefresh cache group cannot contain a WITH ID clause unless the cache group is dynamic.

You cannot use the COMMIT EVERY n ROWS clause with the WITH ID clause.

Initiating an immediate autorefresh

If the Oracle Database tables have been updated with data that needs to be applied to cache tables without waiting for the next autorefresh operation, you can call the ttCacheAutorefresh built-in procedure. The ttCacheAutorefresh built-in procedure initiates an immediate refresh operation and resets the autorefresh cycle to start at the moment you invoke ttCacheAutorefresh. The refresh operation is full or incremental depending on how the cache group is configured. The autorefresh state must be ON when ttCacheAutorefresh is called.

The autorefresh operation normally refreshes all cache groups sharing the same refresh interval in one transaction in order to preserve transactional consistency across these cache groups. Therefore, although you specify a specific cache group when you call ttCacheAutorefresh, the autorefresh operation occurs in one transaction for all cache groups that share the autorefresh interval with the specified cache group. If there is an existing transaction with table locks on objects that belong to the affected cache groups, ttCacheAutofresh returns an error without taking any action.

You can choose to run ttCacheAutorefresh asynchronously (the default) or synchronously. In synchronous mode, ttCacheAutorefresh returns an error if the refresh operation fails.

After calling ttCacheAutorefresh, you must commit or roll back the transaction before subsequent work can be performed.

Example 5-6 Calling ttCacheAutorefresh

This example calls ttCacheAutorefresh for the ttuser.western_customers cache group, using asynchronous mode.

Command> call ttCacheAutorefresh('ttuser', 'western_customers');

Loading and refreshing a multiple-table cache group

If you are loading or refreshing a multiple-table cache group while the cached Oracle Database tables are concurrently being updated, set the isolation level in the TimesTen database to serializable before issuing the LOAD CACHE GROUP or REFRESH CACHE GROUP statement. This causes TimesTen to query the cached Oracle Database tables in a serializable fashion during the load or refresh operation so that the loaded or refreshed cache instances in the cache tables are guaranteed to be transactionally consistent with the corresponding rows in the cached Oracle Database tables. After you have loaded or refreshed the cache group, set the isolation level back to read committed for better concurrency when accessing elements in the TimesTen database.

Improving the performance of loading or refreshing a large number of cache instances

You can improve the performance of loading or refreshing a large number of cache instances into a cache group by using the PARALLEL clause of the LOAD CACHE GROUP or REFRESH CACHE GROUP statement. Specify the number of threads to use when processing the load or refresh operation. You can specify 1 to 10 threads. One thread fetches rows from the cached Oracle Database tables, while the other threads insert the rows into the TimesTen cache tables. Do not specify more threads than the number of CPUs available on your system or you may encounter decreased performance than if you had not used the PARALLEL clause.

Note:
You cannot use the WITH ID clause with the PARALLEL clause. You can use the COMMIT EVERY n ROWS clause with the PARALLEL clause as long as n is greater than 0. In addition, you cannot use the PARALLEL clause for read-only dynamic cache groups or when database level locking is enabled. For more details, see "REFRESH CACHE GROUP" in the Oracle TimesTen In-Memory Database SQL Reference.

Example 5-7 Refreshing a cache group using a PARALLEL clause

The following statement refreshes cache instances in the TimesTen cache tables within the western_customers cache group from the cached Oracle Database tables using one thread to fetch rows from the cached Oracle Database tables and three threads to insert the rows into the cache tables:

REFRESH CACHE GROUP western_customers COMMIT EVERY 256 ROWS PARALLEL 4;

Example of manually loading and refreshing an explicitly loaded cache group

The following is the definition of the Oracle Database table that is to be cached in an explicitly loaded AWT cache group. The Oracle Database table is owned by the schema user oratt.

CREATE TABLE customer
(cust_num NUMBER(6) NOT NULL PRIMARY KEY,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100));

The following is the data in the oratt.customer cached Oracle Database table.

CUST_NUM   REGION    NAME              ADDRESS
--------   -------   ---------------   ---------------------------
1   West      Frank Edwards     100 Pine St. Portland OR
2   East      Angela Wilkins    356 Olive St. Boston MA
3   Midwest   Stephen Johnson   7638 Walker Dr. Chicago IL

The following statement creates an explicitly loaded AWT cache group new_customers that caches the oratt.customer table:

CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP new_customers
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num));

The oratt.customer TimesTen cache table is initially empty.

Command> SELECT * FROM oratt.customer;
0 rows found.

The following LOAD CACHE GROUP statement loads the three cache instances from the cached Oracle Database table into the TimesTen cache table:

Command> LOAD CACHE GROUP new_customers COMMIT EVERY 256 ROWS;
3 cache instances affected.
Command> SELECT * FROM oratt.customer;
< 1, West, Frank Edwards, 100 Pine St. Portland OR >
< 2, East, Angela Wilkins, 356 Olive St. Boston MA >
< 3, Midwest, Stephen Johnson, 7638 Walker Dr. Chicago IL >

Update the cached Oracle Database table by inserting a new row, updating an existing row, and deleting an existing row:

SQL> INSERT INTO customer
2  VALUES (4, 'East', 'Roberta Simon', '3667 Park Ave. New York NY');
SQL> UPDATE customer SET name = 'Angela Peterson' WHERE cust_num = 2;
SQL> DELETE FROM customer WHERE cust_num = 3;
SQL> COMMIT;
SQL> SELECT * FROM customer;
CUST_NUM   REGION    NAME              ADDRESS
--------   -------   ---------------   ---------------------------
1   West      Frank Edwards     100 Pine St. Portland OR
2   East      Angela Peterson   356 Olive St. Boston MA
4   East      Roberta Simon     3667 Park Ave. New York NY

A REFRESH CACHE GROUP statement issued on an explicitly loaded cache group is processed by unloading and then reloading the cache group. As a result, the cache instances in the cache table matches the rows in the cached Oracle Database table.

Command> REFRESH CACHE GROUP new_customers COMMIT EVERY 256 ROWS;
3 cache instance affected.
Command> SELECT * FROM oratt.customer;
< 1, West, Frank Edwards, 100 Pine St. Portland OR >
< 2, East, Angela Peterson, 356 Olive St. Boston MA >
< 4, East, Roberta Simon, 3667 Park Ave. New York NY >

Example of manually loading and refreshing a dynamic cache group

The following is the definition of the Oracle Database table that is to be cached in a dynamic AWT cache group. The Oracle Database table is owned by the schema user oratt.

CREATE TABLE customer
(cust_num NUMBER(6) NOT NULL PRIMARY KEY,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100));

The following is the data in the oratt.customer cached Oracle Database table.

CUST_NUM   REGION    NAME              ADDRESS
--------   -------   ---------------   ---------------------------
1   West      Frank Edwards     100 Pine St. Portland OR
2   East      Angela Wilkins    356 Olive St. Boston MA
3   Midwest   Stephen Johnson   7638 Walker Dr. Chicago IL

The following statement creates a dynamic AWT cache group new_customers that caches the oratt.customer table:

CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH CACHE GROUP new_customers
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num));

The oratt.customer TimesTen cache table is initially empty:

Command> SELECT * FROM oratt.customer;
0 rows found.

The following LOAD CACHE GROUP statement loads the three cache instances from the cached Oracle Database table into the TimesTen cache table:

Command> LOAD CACHE GROUP new_customers COMMIT EVERY 256 ROWS;
3 cache instances affected.
Command> SELECT * FROM oratt.customer;
< 1, West, Frank Edwards, 100 Pine St. Portland OR >
< 2, East, Angela Wilkins, 356 Olive St. Boston MA >
< 3, Midwest, Stephen Johnson, 7638 Walker Dr. Chicago IL >

Update the cached Oracle Database table by inserting a new row, updating an existing row, and deleting an existing row:

SQL> INSERT INTO customer
2  VALUES (4, 'East', 'Roberta Simon', '3667 Park Ave. New York NY');
SQL> UPDATE customer SET name = 'Angela Peterson' WHERE cust_num = 2;
SQL> DELETE FROM customer WHERE cust_num = 3;
SQL> COMMIT;
SQL> SELECT * FROM customer;
CUST_NUM   REGION    NAME              ADDRESS
--------   -------   ---------------   ---------------------------
1   West      Frank Edwards     100 Pine St. Portland OR
2   East      Angela Peterson   356 Olive St. Boston MA
4   East      Roberta Simon     3667 Park Ave. New York NY

A REFRESH CACHE GROUP statement issued on a dynamic cache group only refreshes committed updates and deletes on the cached Oracle Database tables into the cache tables. New cache instances are not loaded into the cache tables. Therefore, only existing cache instances are refreshed. As a result, the number of cache instances in the cache tables are either fewer than or the same as the number of rows in the cached Oracle Database tables.

Command> REFRESH CACHE GROUP new_customers COMMIT EVERY 256 ROWS;
2 cache instances affected.
Command> SELECT * FROM oratt.customer;
< 1, West, Frank Edwards, 100 Pine St. Portland OR >
< 2, East, Angela Peterson, 356 Olive St. Boston MA >

A subsequent LOAD CACHE GROUP statement loads one cache instance from the cached Oracle Database table into the TimesTen cache table because only committed inserts are loaded into the cache table. Therefore, only new cache instances are loaded. Cache instances that already exist in the cache tables are not changed because of a LOAD CACHE GROUP statement, even if the corresponding rows in the cached Oracle Database tables were updated or deleted.

Command> LOAD CACHE GROUP new_customers COMMIT EVERY 256 ROWS;
1 cache instance affected.
Command> SELECT * FROM oratt.customer;
< 1, West, Frank Edwards, 100 Pine St. Portland OR >
< 2, East, Angela Peterson, 356 Olive St. Boston MA >
< 4, East, Roberta Simon, 3667 Park Ave. New York NY >

Dynamically loading a cache instance

In a dynamic cache group, data is automatically loaded into the TimesTen cache tables from the cached Oracle Database tables when a qualifying SELECT, INSERT, UPDATE, or DELETE statement is issued on one of the cache tables and the data does not exist in the cache table but does exist in the cached Oracle Database table.

Note:
If the Oracle database is down, the following error is returned:

5219: Temporary Oracle connection failure error in OCISessionBegin():
ORA-01034: ORACLE not available

Note:
Dynamic load can only be performed for dynamic cache groups if the DynamicLoadEnable connection attribute is enabled. See "Dynamic load configuration" for more details.

A dynamic load retrieves a single cache instance that is either automatically loaded from the Oracle database to the TimesTen database or, for dynamic global cache groups, transferred from the grid member that owns the instance to the requesting grid member. A cache instance consists of row from the root table of any cache group (that is uniquely identified by either a primary key or a unique index on the root table) and all related rows in the child tables associated by foreign key relationships.

If a row in the cached Oracle Database table satisfies the WHERE clause, the entire associated cache instance is loaded in order to maintain the defined relationships between primary keys and foreign keys of the parent and child tables. A dynamic load operation cannot load more than one row into the root table of any cache group. Only cache instances whose rows satisfy the WHERE clause of the cache table definitions are loaded.

The WHERE clause must specify one of the following for a dynamic load to occur:

- An equality condition with constants and/or parameters on all columns of a primary key or a foreign key of any table of the cache group. If more than one table of a cache group is referenced, each must be connected by an equality condition on the primary or foreign key relationship.

- A mixture of equality or IS NULL conditions on all columns of a unique index, provided that you use at least one equality condition. That is, you can perform a dynamic load where some columns of the unique index are NULL. The unique index must be created on the root table of the cache group.

Note:
Dynamic loading based on a primary key search of the root table performs faster than primary key searches on a child table or foreign key searches on a child table.

The dynamic load is executed in a different transaction than the user transaction that triggers the dynamic load. The dynamic load transaction is committed before the SQL statement that triggers the dynamic load has finished execution. Thus, if the user transaction is rolled back, the dynamically loaded data remains in the cache group.

With global cache groups, the TimesTen database must be attached to a cache grid before dynamic load is allowed with these cache groups. See "Global cache groups" for more information about global cache groups and attaching a TimesTen database to a cache grid.

The following sections describes dynamic load for cache groups:

- Dynamic load configuration

- Dynamic load guidelines

- Examples of dynamically loading a cache instance

- Return dynamic load errors

Dynamic load configuration

Dynamic load can be configured with the DynamicLoadEnable connection attribute as follows:

- 0 - Disables dynamic load of Oracle Database data to TimesTen dynamic cache groups for the current connection.

- 1 (default) - Enables dynamic load of Oracle Database data to a single TimesTen dynamic cache group per statement for the current connection. The statement must reference tables of only one dynamic cache group and only in the main query. The statement can also reference non-cache tables. Only one cache instance can be loaded.

- 2 - Enables dynamic load of Oracle Database data to one or multiple TimesTen dynamic cache groups per statement for the current connection. The referenced tables can exist within multiple cache groups. All cache groups referenced in the main query are to be dynamically loaded; any cache groups referenced solely in a subquery are to be ignored for dynamic load. The statement can also reference non-cache tables. Only one cache instance can be loaded.

Set the appropriate value in the DynamicLoadEnable connection attribute to configure the type of dynamic loading for all cache tables in dynamic cache groups that are accessed within a particular connection.

To enable or disable dynamic loading for a particular transaction, you can set the DynamicLoadEnable optimizer hint. However, the DynamicLoadEnable connection attribute is the only method for configuring what type of dynamic load is enabled.

You can set the DynamicLoadEnable optimizer hint with one of the following methods:

- Use the ttIsql utility set dynamicloadenable command.

- Call the ttOptSetFlag built-in procedure with the DynamicLoadEnable flag set to the desired value. The following example sets dynamic loading to 1.

call ttOptSetFlag('DynamicLoadEnable', 1)

Note:
For more details, see "DynamicLoadEnable", "ttIsql" or "ttOptSetFlag" in the Oracle TimesTen In-Memory Database Reference.
You can also set connection attributes with the SQLSetConnectOption ODBC function. See "Option support for SQLSetConnectOption and SQLGetConnectOption" in the Oracle TimesTen In-Memory Database C Developer's Guide for more details.

Dynamic load guidelines

Dynamic load retrieves at most one cache instance for each cache group referenced in the main query. This section details the guidelines under which dynamic load occurs.

Note:
Examples for these guidelines are provided in "Examples of dynamically loading a cache instance".

Dynamic load is available only for the following types of statements issued on a cache table in a dynamic cache group:

- When an INSERT statement inserts values into any of the child tables of a cache instance that does not currently exist in the TimesTen tables, the cache instance to which the new row belongs dynamically loads. The insert operation for the new child row is propagated to the cached Oracle Database table.

- SELECT, UPDATE, or DELETE statements require that the WHERE clause have the conditions as stated in "Dynamically loading a cache instance".

The SELECT, UPDATE, or DELETE statements for which dynamic load is available must satisfy the following conditions:

- If the statement contains a subquery, only the cache group with tables referenced in the main query are considered for a dynamic load.

- If the statement references multiple tables of the cache group, the statement must include an equality join condition between the primary keys and foreign keys for all parent and child relationships.

- The statement cannot contain the UNION, INTERSECT, or MINUS set operators.

- The statement can reference non-cache tables.

- By default, the statement can reference cache tables from only one dynamic cache group. This behavior is enabled when DynamicLoadEnable is set to 1. However, if DynamicLoadEnable is set to 2, the statement can reference cache tables from multiple dynamic cache groups. See "Dynamic load configuration" for more information.

Dynamic load behavior depends on the setting of DynamicLoadEnable. The following describes the rules that are evaluated to determine if a dynamic load occurs. These rules are followed when DynamicLoadEnable is set to either 1 or 2.

- Dynamic load does not occur for a cache group if any table of the cache group is specified more than once in any FROM clause.

- Only the conditions explicitly specified in the query are considered for dynamic load, which excludes any derived conditions.

- If any cache group is referenced only in a subquery, it is not considered for a dynamic load.

- If the cache group has a time-based aging policy defined, the timestamp in the root table's row must be within the aging policy's lifetime in order for the cache instance to be loaded. See "Implementing aging in a cache group" for information about defining an aging policy on a cache group.

- When using an active standby pair replication scheme, dynamic load cannot occur in any subscriber.

When dynamic load is enabled with setting DynamicLoadEnable to 2, you can include multiple dynamic cache groups in the statement. The rules for this situation that determines if a dynamic load occurs are as follows:

- If multiple cache groups exist within in a query, dynamic load is considered for the cache groups that meet the required conditions for a dynamic load. Dynamic load is not considered for any cache groups that do not meet dynamic load conditions.

- If tables of any dynamic cache group are referenced in the main query, they are considered for dynamic load, even if other tables in any cache group are referenced in the subquery.

The following considerations can affect dynamic load:

- If tables within multiple cache groups or non-cache group tables are specified in the main query, the join order influences if the cache instance is loaded. If during the execution of the query, a dynamic load is possible and necessary to produce the query results, the dynamic load occurs. However, if no rows are returned, then some or all of the cache instances are not dynamically loaded.

- If a statement specifies more than the dynamic load condition on tables of a cache group, the cache instance may be dynamically loaded even though the additional conditions are not qualified for the statement.

Examples of dynamically loading a cache instance

The following is the definition of the Oracle Database tables that are to be cached in a dynamic AWT cache group. The Oracle Database table is owned by the schema user oratt.

CREATE TABLE customer
(cust_num NUMBER(6) NOT NULL PRIMARY KEY,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100));

CREATE TABLE orders
(ord_num      NUMBER(10) NOT NULL PRIMARY KEY,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL);

CREATE TABLE orderdetails
(orderid  NUMBER(10) NOT NULL,
itemid   NUMBER(8) NOT NULL,
quantity NUMBER(4) NOT NULL,
PRIMARY KEY (orderid, itemid));

For example, the following data is in the oratt.customer cached Oracle Database table.

CUST_NUM   REGION    NAME              ADDRESS
--------   -------   ---------------   ---------------------------
1   West      Frank Edwards     100 Pine St., Portland OR
2   East      Angela Wilkins    356 Olive St., Boston MA
3   Midwest   Stephen Johnson   7638 Walker Dr., Chicago IL

The following statement creates a dynamic AWT cache group new_customers that caches the oratt.customer, oratt.orders, and oratt.orderdetails tables:

CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH CACHE GROUP new_customers
FROM oratt.customer
(cust_num NUMBER(6) NOT NULL,
region   VARCHAR2(10),
name     VARCHAR2(50),
address  VARCHAR2(100),
PRIMARY KEY(cust_num)),
oratt.orders
(ord_num      NUMBER(10) NOT NULL,
cust_num     NUMBER(6) NOT NULL,
when_placed  DATE NOT NULL,
when_shipped DATE NOT NULL,
PRIMARY KEY(ord_num),
FOREIGN KEY(cust_num) REFERENCES oratt.customer(cust_num)),
oratt.orderdetails
(orderid  NUMBER(10) NOT NULL,
itemid   NUMBER(8) NOT NULL,
quantity NUMBER(4) NOT NULL,
PRIMARY KEY(orderid, itemid),
FOREIGN KEY(orderid) REFERENCES oratt.orders(order_num));

The following examples can be used when DynamicLoadEnable is set to 1:

The oratt.customer TimesTen cache table is initially empty:

Command> SELECT * FROM oratt.customer;
0 rows found.

The following SELECT statement with an equality condition on the primary key for the oratt.customer table results in a dynamic load:

Command> SELECT * FROM oratt.customer WHERE cust_num = 1;
< 1, West, Frank Edwards, 100 Pine St., Portland OR >

However, if you do not use an equality condition on the primary key, no dynamic load occurs:

Command> SELECT * FROM oratt.customer WHERE cust_num IN (1,2);

The following example contains equality expressions on all of the primary key columns for a primary key composite. The orderdetails table has a composite primary key of orderid and itemid.

UPDATE oratt.orderdetails SET quantity = 5 WHERE orderid=2280 AND itemid=663;

The following example shows an INSERT into the orders child table, which initiates a dynamic load. However, if you tried to insert into the customer table, which is the parent, no dynamic load occurs.

INSERT INTO orders VALUES(1,1, DATE '2012-01-25', DATE '2012-01-30');

The following UPDATE statement dynamically loads one cache instance from the cached Oracle Database table into the TimesTen cache table, updates the instance in the cache table, and then automatically propagates the update to the cached Oracle Database table:

Command> UPDATE oratt.customer SET name = 'Angela Peterson' WHERE cust_num = 2;
Command> SELECT * FROM oratt.customer;
< 1, West, Frank Edwards, 100 Pine St., Portland OR >
< 2, East, Angela Peterson, 356 Olive St., Boston MA >

The following is the updated data in the oratt.customer cached Oracle Database table:

CUST_NUM   REGION    NAME              ADDRESS
--------   -------   ---------------   ---------------------------
1   West      Frank Edwards     100 Pine St., Portland OR
2   East      Angela Peterson   356 Olive St., Boston MA
3   Midwest   Stephen Johnson   7638 Walker Dr., Chicago IL

The following DELETE statement dynamically loads one cache instance from the cached Oracle Database table into the TimesTen cache table, deletes the instance from the cache table, and then automatically propagates the delete to the cached Oracle Database table:

Command> DELETE FROM oratt.customer WHERE cust_num = 3;
Command> SELECT * FROM oratt.customer;
< 1, West, Frank Edwards, 100 Pine St., Portland OR >
< 2, East, Angela Peterson, 356 Olive St., Boston MA >

The following is the updated data in the oratt.customer cached Oracle Database table.

CUST_NUM   REGION    NAME              ADDRESS
--------   -------   ---------------   ---------------------------
1   West      Frank Edwards     100 Pine St., Portland OR
2   East      Angela Peterson   356 Olive St., Boston MA

The following is an example of a dynamic load performed using all columns of a unique index on the root table. The departments table is defined in a dynamic AWT cache group. A unique index is created on this cache group consisting of the manager_id and location_id.

The following creates the departments table on the Oracle database.

Command> CREATE TABLE departments(
> department_id INT NOT NULL PRIMARY KEY,
> department_name VARCHAR(10) NOT NULL,
> technical_lead INT NOT NULL,
> manager_id INT,
> location_id INT NOT NULL);

The following creates the dynamic AWT cache group and a unique index on the dept_cg root table:

Command> CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH CACHE GROUP dept_cg
> FROM departments
> (department_id INT NOT NULL PRIMARY KEY,
>  department_name VARCHAR(10) NOT NULL,
>  technical_lead INT NOT NULL,
>  manager_id INT, location_id INT NOT NULL);

Command> CREATE UNIQUE INDEX dept_idx ON departments(manager_id, location_id);

The following inserts three records into the departments table on the Oracle database:

Command> insert into departments values (1, 'acct', 1, 1, 100);
1 row inserted.
Command> insert into departments values (2, 'legal', 2, 2, 200);
1 row inserted.
Command> insert into departments values (3, 'owner', 3, NULL, 300);
1 row inserted.
Command> commit;

On TimesTen, dynamically load a cache instance based on the unique index:

Command> SELECT * FROM departments;
0 rows found.
Command> SELECT * FROM departments WHERE manager_id IS NULL AND location_id=300;
< 3, owner, 3, <NULL>, 300 >
1 row found.
Command> SELECT * FROM departments;
< 3, owner, 3, <NULL>, 300 >
1 row found.
Command> SELECT * FROM departments WHERE manager_id=2 AND location_id=200;
< 2, legal, 2, 2, 200 >
1 row found.
Command> SELECT * FROM departments;
< 2, legal, 2, 2, 200 >
< 3, owner, 3, <NULL>, 300 >
2 rows found.

The following examples demonstrate how to use dynamic load when referencing tables across multiple cache groups, which is enabled when DynamicLoadEnable is set to 2.

The following statements create multiple dynamic AWT cache groups, each with one or more tables that are cached from the Oracle database.

CREATE DYNAMIC CACHE GROUP cachegrp
FROM table1(x1 INT PRIMARY KEY, y1 INT);

CREATE DYNAMIC CACHE GROUP cachegrp2
FROM table2(x2 INT PRIMARY KEY, y2 INT),
table3(x3 INT PRIMARY KEY, y3 INT,
FOREIGN KEY(y3) REFERENCES table2(x2);

CREATE DYNAMIC CACHE GROUP cachegrp3
FROM table4(x4 INT PRIMARY KEY, y4 INT);

CREATE TABLE table5
(x5 INT PRIMAY KEY,y5 INT);

The following example shows that no dynamic load occurs, even though the optimizer may derive that x1 should be equated to 1:

SELECT * FROM table1, table5 WHERE x5=1 AND x5=x1;

Dynamic load is considered for the cache instance from table2 within cachegrp2 since table2 is referenced in the main query.

SELECT * FROM table5, table2
WHERE x5 IN (SELECT y2 FROM table2, table3 where x2=1 and x2=y3);

The cache instance in the cachegrp2 cache group is not considered for a dynamic load because all of its tables are referenced in the subquery.

SELECT * FROM table5
WHERE x5 IN
(SELECT y3 FROM table2, table3 WHERE x2=1 AND x2=y3);

In the following example, if the row that would be retrieved from table1 where x1=1 is not already in the cache, whether the cache instance from table1 is loaded depends on the join order. If the join order is 'table5 table1,' the cache instance from table1 is loaded if and only if there is a row in table5 for which x5=1. If the join order is 'table1 table5', then the cache instance from table1 is always loaded.

SELECT * FROM table1, table5 WHERE x1=1 AND x5=1;

A row (1,1) may be loaded for table1, but the SELECT does not return any rows.

SELECT * FROM table1 WHERE x1=1 AND y1>1;

Return dynamic load errors

You can configure TimesTen to return an error if a SELECT, UPDATE or DELETE statement does not meet the requirements stated in "Dynamic load guidelines". The DynamicLoadErrorMode connection attribute controls what happens when an application executes a SQL operation against a dynamic cache group and the SQL operation cannot use dynamic load in a particular connection.

- When DynamicLoadErrorMode is set to a value of 0, dynamic load happens to any cache group referenced in the query that is qualified for dynamic load. Cache groups that do not qualify are not dynamically loaded and no errors are returned. When DynamicLoadEnable=1, no dynamic load occurs if the query references more than one cache group.

- When DynamicLoadErrorMode is set to a value of 1, a query fails with an error if any dynamic cache group referenced in the query is not qualified for dynamic load. The error indicates the reason why the dynamic load cannot occur.

To set the connection attribute solely for a particular transaction, use one of the following:

- Use the ttIsql utility set dynamicloaderrormode 1 command.

- Call the ttOptSetFlag built-in procedure with the DynamicLoadErrorMode flag and the optimizer value set to 1.

call ttOptSetFlag('DynamicLoadErrorMode', 1)

Call the ttOptSetFlag built-in procedure with the DynamicLoadErrorMode flag and the optimizer value set to 0 to suppress error reporting when a statement does not comply with dynamic load requirements.

Flushing a user managed cache group

The FLUSH CACHE GROUP statement manually propagates committed inserts and updates on TimesTen cache tables in a user managed cache group to the cached Oracle Database tables. Deletes are not flushed or manually propagated. Committed inserts and updates on cache tables that use the PROPAGATE cache table attribute cannot be flushed to the cached Oracle Database tables because these operations are already automatically propagated to the Oracle database.

With automatic propagation, committed inserts, updates and deletes are propagated to the Oracle database in the order they were committed in TimesTen. A flush operation can manually propagate multiple committed transactions on cache tables to the cached Oracle Database tables.

You cannot flush a user managed cache group that uses the AUTOREFRESH cache group attribute.

You can flush a user managed cache group if at least one of its cache tables uses neither the PROPAGATE nor the READONLY cache table attribute.

You can use a WHERE clause or WITH ID clause in a FLUSH CACHE GROUP statement to restrict the rows to be flushed to the cached Oracle Database tables. See the "FLUSH CACHE GROUP" statement in Oracle TimesTen In-Memory Database SQL Reference for more information.

Example 5-8 Flushing a cache group

The following statement manually propagates committed insert and update operations on the TimesTen cache tables in the western_customers cache group to the cached Oracle Database tables:

FLUSH CACHE GROUP western_customers;

Unloading a cache group

You can delete some or all cache instances from the cache tables in a cache group with the UNLOAD CACHE GROUP statement. Unlike the DROP CACHE GROUP statement, the cache tables themselves are not dropped when a cache group is unloaded.

Use caution when using the UNLOAD CACHE GROUP statement with autorefresh cache groups. An unloaded row can reappear in the cache table as the result of an autorefresh operation if the row, or its related parent or child rows, are updated in the cached Oracle Database table.

Execution of the UNLOAD CACHE GROUP statement for an AWT cache group waits until updates on the rows have been propagated to the Oracle database.

To prevent an unload operation from processing a large number of cache instances within a single transaction, which could reduce concurrency and throughput, use the COMMIT EVERY n ROWS clause to specify a commit frequency.

Note:
For more information, see "UNLOAD CACHE GROUP" in the Oracle TimesTen In-Memory Database SQL Reference.

Example 5-9 Unloading cache groups

The following statement unloads all cache instances from all cache tables in the customer_orders cache group. A commit frequency is specified, so the operations is performed over several transactions by committing every 256 rows:

UNLOAD CACHE GROUP customer_orders COMMIT EVERY 256 ROWS;

The following statement unloads all cache instances from all cache tables in the customer_orders cache group in a single transaction. A single transaction should only be used if the data within customer_orders is small:

UNLOAD CACHE GROUP customer_orders;

The following equivalent statements delete the cache instance for customer number 227 from the cache tables in the new_customers cache group:

UNLOAD CACHE GROUP new_customers WITH ID (227);
UNLOAD CACHE GROUP new_customers WHERE (oratt.customer.cust_num = 227);

Unloading a cache group across all grid members

You can unload a cache group in all members of a cache grid by setting an optimizer flag. Before executing the UNLOAD CACHE GROUP statement, call the ttOptSetFlag built-in procedure and set the GlobalProcessing optimizer flag to 1:

Note:
The unload operation does not execute across multiple grid nodes when using the COMMIT EVERY n ROWS clause, regardless of the state of the GlobalProcessing optimizer flag.

CALL ttOptSetFlag('GlobalProcessing', 1);

Consider this statement:

UNLOAD CACHE GROUP customer WHERE customer_id=54321;

A local unload operation removes the customer record only if the record exists on the node where the statement is executed. A global unload operation removes the customer record regardless of which node contains the record.

Determining the number of cache instances affected by an operation

You can use the following mechanisms to determine how many cache instances were loaded by a LOAD CACHE GROUP statement, refreshed by a REFRESH CACHE GROUP statement, flushed by a FLUSH CACHE GROUP statement, or unloaded by an UNLOAD CACHE GROUP statement:

- Call the SQLRowCount() ODBC function.

- Invoke the Statement.getUpdateCount() JDBC method.

- Call the OCIAttrGet() OCI function with the OCI_ATTR_ROW_COUNT option.

Setting a passthrough level

When an application issues statements on a TimesTen connection, the statement can be executed in the TimesTen database or passed through to the Oracle database for execution. Whether the statement is executed in the TimesTen or Oracle database depends on the composition of the statement and the setting of the PassThrough connection attribute. You can set the PassThrough connection attribute to define which statements are to be executed locally in TimesTen and which are to be redirected to the Oracle database for execution.

When appropriate within passthrough levels 1 through 5, TimesTen connects to the Oracle database using the current user's credentials as the user name and the OraclePwd connection attribute as the Oracle password.

Note:
A transaction that contains operations that are replicated with RETURN TWOSAFE cannot have a PassThrough setting greater than 0. If PassThrough is greater than 0, an error is returned and the transaction must be rolled back.
When PassThrough is set to 0, 1, or 2, the following behavior occurs when a dynamic load condition exists:

- A dynamic load can occur for a SELECT operation on cache tables in any dynamic cache group type.

- A dynamic load for an INSERT, UPDATE, or DELETE operation can only occur on cached tables with dynamic AWT or SWT cache groups.

See "Dynamically loading a cache instance" for more details on dynamic load.

PassThrough=0

PassThrough=0 is the default setting and specifies that all statements are to be executed in the TimesTen database. Figure 5-1 shows that Table A is updated on the TimesTen database. Table F cannot be updated because it does not exist in TimesTen.

Figure 5-1 PassThrough=0

PassThrough=1

Set PassThrough=1 to specify that a statement that references a table that does not exist in the TimesTen database is passed through to the Oracle database for execution. No DDL statements are passed through to the Oracle database.

If TimesTen cannot parse a SELECT statement because it includes keywords that do not exist in TimesTen SQL or because it includes syntax errors, it passes the statement to the Oracle database. If TimesTen cannot parse INSERT, UPDATE or DELETE statements, TimesTen returns an error and the statement is not passed through to the Oracle database.

Figure 5-2 shows that Table A is updated in the TimesTen database, while Table G is updated in the Oracle database because Table G does not exist in the TimesTen database.

Figure 5-2 PassThrough=1

PassThrough=2

PassThrough=2 specifies that INSERT, UPDATE and DELETE statements are passed through to the Oracle database for read-only cache groups and user managed cache groups that use the READONLY cache table attribute. Otherwise, Passthrough=1 behavior applies.

Note:
You are responsible in preventing conflicts that may occur if you update the same row in a TimesTen cache table as another user updates the cached Oracle Database table concurrently.

Figure 5-3 shows that updates to Table A and Table G in a read-only cache group are passed through to the Oracle database.

Figure 5-3 PassThrough=2

PassThrough=3

PassThrough=3 specifies that all statements are passed through to the Oracle database for execution, except that INSERT, UPDATE and DELETE statements issued on cache tables in a dynamic AWT global cache group result in a TimesTen error.

Figure 5-4 shows that Table A is updated on the Oracle database for a read-only or updatable cache group. A SELECT statement that references Table G is also passed through to the Oracle database. A SELECT statement that references Table C in a dynamic AWT global cache group is passed through to the Oracle database.

Figure 5-4 PassThrough=3

PassThrough=4

PassThrough=4 specifies that SELECT statements issued on cache tables in a dynamic AWT global cache group that do not satisfy the criteria for a dynamic load query are passed through to the Oracle database for execution. Otherwise, statements are executed in the TimesTen database. See "Dynamic load guidelines" for the criteria for a dynamic load SELECT statement.

Figure 5-5 shows that Table A in an updatable cache group is updated in the TimesTen database. The figure also shows a SELECT statement issued on a dynamic AWT global cache group that does not satisfy the criteria for a dynamic load SELECT statement and is passed through to the Oracle database for execution.

Figure 5-5 PassThrough=4

PassThrough=5

PassThrough=5 specifies that SELECT statements issued on cache tables in a dynamic AWT global cache group that do not satisfy the criteria for a dynamic load query are passed through to the Oracle database for execution when all committed updates on cache tables in dynamic AWT global cache groups by previous transactions within the connection have been propagated to the Oracle database. Otherwise statements are executed in the TimesTen database. See "Dynamic load guidelines" for the criteria for a dynamic load SELECT statement.

Figure 5-6 shows that Table A in an updatable cache group is updated in the TimesTen database. The figure also shows a SELECT statement issued on a dynamic AWT global cache group that does not satisfy the criteria for a dynamic load SELECT statement and is passed through to the Oracle database for execution after all committed updates on cache tables in dynamic AWT global cache groups by previous transactions within the connection have been propagated to the Oracle database.

Figure 5-6 PassThrough=5

Considerations for using passthrough

Passing through update operations to the Oracle database for execution is not recommended when issued on cache tables in an AWT or SWT cache group.

- Committed updates on cache tables in an AWT cache group are automatically propagated to the cached Oracle Database tables in asynchronous fashion. However, passing through an update operation to the Oracle database for execution within the same transaction as the update on the cache table in the AWT cache group renders the propagate of the cache table update synchronous, which may have undesired results.

- Committed updates on cache tables in an SWT cache group can result in self-deadlocks if, within the same transaction, updates on the same tables are passed through to the Oracle database for execution.

A PL/SQL block cannot be passed through to the Oracle database for execution. Also, you cannot pass through to Oracle Database for execution a reference to a stored procedure or function that is defined in the Oracle database but not in the TimesTen database.

For more information about how the PassThrough connection attribute setting determines which statements are executed in the TimesTen database and which are passed through to the Oracle database for execution and under what circumstances, see "PassThrough" in Oracle TimesTen In-Memory Database Reference.

Note:
The passthrough feature uses OCI to communicate with the Oracle database. The OCI diagnostic framework installs signal handlers that may impact signal handling that you use in your application. You can disable OCI signal handling by setting DIAG_SIGHANDLER_ENABLED=FALSE in the sqlnet.ora file. Refer to "Fault Diagnosability in OCI" in Oracle Call Interface Programmer's Guide for information.

Changing the passthrough level for a connection or transaction

You can override the current passthrough level using the ttIsql utility's set passthrough command which applies to the current transaction.

You can also override the setting for a specific transaction by calling the ttOptSetFlag built-in procedure with the PassThrough flag. The following procedure call sets the passthrough level to 3:

CALL ttOptSetFlag('PassThrough', 3);

The PassThrough flag setting takes effect when a statement is prepared and it is the setting that is used when the statement is executed even if the setting has changed from the time the statement was prepared to when the statement is executed. After the transaction has been committed or rolled back, the original connection setting takes effect for all subsequently prepared statements.

6 Creating Other Cache Grid Members

The following sections describe the tasks for creating a second standalone TimesTen database and an active standby pair, and attaching these members to the cache grid that was created in Chapter 3, "Setting Up a Caching Infrastructure".

- Creating and configuring a subsequent standalone TimesTen database

- Replicating cache tables

- Example of data sharing among the grid members

- Performing global queries on a cache grid

- Adding other elements to a cache grid or grid member

Note:
If you are planning to use Oracle Clusterware to manage active standby pairs in a cache grid, see "Using Oracle Clusterware with a TimesTen cache grid" in Oracle TimesTen In-Memory Database Replication Guide.
Also see "Restricted commands and SQL statements" in Oracle TimesTen In-Memory Database Replication Guide. Use the ttCWAdmin utility to manage the active standby pair grid members instead of the built-in procedures discussed in this chapter.

Creating and configuring a subsequent standalone TimesTen database

The following is the definition of the cachealone2 DSN for the second standalone TimesTen database that becomes a member of the ttGrid cache grid:

[cachealone2]
DataStore=/users/OracleCache/alone2
PermSize=64
OracleNetServiceName=orcl
DatabaseCharacterSet=WE8ISO8859P1
CacheGridEnable=1

Start the ttIsql utility and connect to the cachealone2 DSN as the instance administrator to create the database. Then create the cache manager user cacheuser whose name needs to be the same as a companion Oracle Database user. In this example, the cache administration user is acting as the companion Oracle Database user to the cache manager user.

Then create a cache table user oratt whose name is the same as the Oracle Database schema user who owns the Oracle Database tables to be cached in the TimesTen database.

% ttIsql cachealone2
Command> CREATE USER cacheuser IDENTIFIED BY timesten;
Command> CREATE USER oratt IDENTIFIED BY timesten;

As the instance administrator, use the ttIsql utility to grant the cache manager user cacheuser the privileges required to perform the operations listed in Example 3-8:

Command> GRANT CREATE SESSION, CACHE_MANAGER, CREATE ANY TABLE TO cacheuser;
Command> exit

Start the ttIsql utility and connect to the cachealone2 DSN as the cache manager user. Set the cache administration user name and password by calling the ttCacheUidPwdSet built-in procedure.

% ttIsql "DSN=cachealone2;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheUidPwdSet('cacheuser','oracle');

Associate the second standalone database to the ttGrid cache grid by calling the ttGridNameSet built-in procedure as the cache manager user:

Command> CALL ttGridNameSet('ttGrid');

The ttGrid cache grid was created from the first standalone TimesTen database. Since the grid already exists, it does not need to be created again.

If desired, you can test the connectivity between the second standalone TimesTen database and the Oracle database using the instructions stated in "Testing the connectivity between the TimesTen and Oracle databases".

Start the cache agent on the second standalone database by calling the ttCacheStart built-in procedure as the cache manager user:

Command> CALL ttCacheStart;

Then, create cache groups in the database as the cache manager user. For example, the following statement creates a dynamic AWT global cache group subscriber_accounts that caches the oratt.subscriber table:

CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH GLOBAL CACHE GROUP subscriber_accounts
FROM oratt.subscriber
(subscriberid       NUMBER(10) NOT NULL PRIMARY KEY,
name               VARCHAR2(100) NOT NULL,
minutes_balance    NUMBER(5) NOT NULL,
last_call_duration NUMBER(4) NOT NULL);

The definition of the oratt.subscriber cached Oracle Database table is shown in "Global cache groups".

If any AWT cache groups were created, start the replication agent on the TimesTen database by calling the ttRepStart built-in procedure as the cache manager user:

Command> CALL ttRepStart;

If any global cache groups were created, the database must attach to the cache grid that it is associated with in order to update the cache tables of the global cache groups. Attaching the database to the grid allows the database to become a member of the grid so that cache instances in the cache tables of the global cache groups can maintain consistency among the databases within the grid.

As the cache manager user, attach the second standalone database to the ttGrid cache grid that it is associated with by calling the ttGridAttach built-in procedure. The node number for a standalone TimesTen database is 1.

In the following example, alone2 is a name that uniquely identifies the grid member, sys2 is the host name of the TimesTen system where the second standalone database resides, and 5002 is the TCP/IP port for the second standalone database's cache agent process:

Command> CALL ttGridAttach(1,'alone2','sys2',5002);
Command> exit

Replicating cache tables

To achieve high availability, configure an active standby pair replication scheme for cache tables in a read-only cache group or an AWT cache group.

An active standby pair that replicates cache tables from one of these cache group types can automatically change the role of a TimesTen database as part of failover and recovery with minimal chance of data loss. Cache groups themselves provide resilience from Oracle database outages, further strengthening system availability. See "Administering an Active Standby Pair with Cache Groups" in Oracle TimesTen In-Memory Database Replication Guide for more information.

An active standby pair replication scheme provides for high availability of a TimesTen database. Multiple grid members provide for high availability of a TimesTen cache grid. Oracle Real Application Clusters (Oracle RAC) provides for high availability of an Oracle database. For more information about using TimesTen Application-Tier Database Cache in an Oracle RAC environment, see "Using TimesTen Application-Tier Database Cache in an Oracle RAC Environment".

Perform the following tasks to configure an active standby pair for TimesTen databases that cache Oracle Database tables:

- Create and configure the active database

- Create and configure the standby database

- Create and configure the read-only subscriber database

Create and configure the active database

The following is the definition of the cacheactive DSN for the active database of the active standby pair that becomes a member of the ttGrid cache grid:

[cacheactive]
DataStore=/users/OracleCache/cacheact
PermSize=64
OracleNetServiceName=orcl
DatabaseCharacterSet=WE8ISO8859P1
CacheGridEnable=1

Start the ttIsql utility and connect to the cacheactive DSN as the instance administrator to create the database. Then create the cache manager user cacheuser whose name is the same as a companion Oracle Database user. In this example, the cache administration user is acting as the companion Oracle Database user.

Then create a cache table user oratt whose name is the same as the Oracle Database schema user who owns the Oracle Database tables to be cached in the TimesTen database.

% ttIsql cacheactive
Command> CREATE USER cacheuser IDENTIFIED BY timesten;
Command> CREATE USER oratt IDENTIFIED BY timesten;

As the instance administrator, use the ttIsql utility to grant the cache manager user cacheuser the privileges required to perform the operations listed in Example 3-8 as well as create an active standby pair replication scheme which requires the ADMIN privilege:

Command> GRANT CREATE SESSION, CACHE_MANAGER,
> CREATE ANY TABLE, ADMIN TO cacheuser;
Command> exit

Start the ttIsql utility and connect to the cacheactive DSN as the cache manager user. Set the cache administration user name and password by calling the ttCacheUidPwdSet built-in procedure.

% ttIsql "DSN=cacheactive;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheUidPwdSet('cacheuser','oracle');

Associate the active database to the ttGrid cache grid by calling the ttGridNameSet built-in procedure as the cache manager user:

Command> CALL ttGridNameSet('ttGrid');

The ttGrid cache grid was created from the first standalone TimesTen database. Since the grid already exists, it does not need to be created again.

If desired, you can test the connectivity between the active database and the Oracle database using the instructions stated in "Testing the connectivity between the TimesTen and Oracle databases".

Start the cache agent on the active database by calling the ttCacheStart built-in procedure as the cache manager user:

Command> CALL ttCacheStart;

Then create cache groups in the database as the cache manager user. For example, the following statement creates a dynamic AWT global cache group subscriber_accounts that caches the oratt.subscriber table:

CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH GLOBAL CACHE GROUP subscriber_accounts
FROM oratt.subscriber
(subscriberid       NUMBER(10) NOT NULL PRIMARY KEY,
name               VARCHAR2(100) NOT NULL,
minutes_balance    NUMBER(5) NOT NULL,
last_call_duration NUMBER(4) NOT NULL);

The definition of the oratt.subscriber cached Oracle Database table is shown in "Global cache groups".

As the cache manager user, create an active standby pair replication scheme in the active database using a CREATE ACTIVE STANDBY PAIR statement.

In the following example, cacheact, cachestand and subscr are the file name prefixes of the checkpoint and transaction log files of the active database, standby database and read-only subscriber database. sys3, sys4 and sys5 are the host names of the TimesTen systems where the active database, standby database and read-only subscriber database reside, respectively.

Command> CREATE ACTIVE STANDBY PAIR cacheact ON "sys3", cachestand ON "sys4"
> SUBSCRIBER subscr ON "sys5";

As the cache manager user, start the replication agent on the active database by calling the ttRepStart built-in procedure. Then declare the database as the active by calling the ttRepStateSet built-in procedure.

Command> CALL ttRepStart;
Command> CALL ttRepStateSet('active');

If any global cache groups were created, the database must attach to the cache grid that it is associated with in order to update the cache tables of the global cache groups. Attaching the database to the grid allows the database to become a member of the grid so that cache instances in the cache tables of the global cache groups can maintain consistency among the databases within the grid.

As the cache manager user, attach the active database to the ttGrid cache grid that it is associated with by calling the ttGridAttach built-in procedure. The node number for an active database is 1.

In the following example:

- cacheact is a name that uniquely identifies the active database grid node.

- cachestand is a name that uniquely identifies the standby database grid node.

- sys3 is the host name of the TimesTen system where the active database resides.

- sys4 is the host name of the TimesTen system where the standby database resides.

- 5003 is the TCP/IP port for the active database's cache agent process.

- 5004 is the TCP/IP port for the standby database's cache agent process.

Command> CALL ttGridAttach(1,'cacheact','sys3',5003,'cachestand','sys4',5004);
Command> exit

Create and configure the standby database

The following is the definition of the cachestandby DSN for the standby database of the active standby pair that becomes a member of the ttGrid cache grid:

[cachestandby]
DataStore=/users/OracleCache/cachestand
PermSize=64
OracleNetServiceName=orcl
DatabaseCharacterSet=WE8ISO8859P1
CacheGridEnable=1

As the instance administrator, create the standby database as a duplicate of the active database by running a ttRepAdmin -duplicate utility command from the standby database system. The instance administrator user name of the active database's and standby database's instances must be identical.

Use the -keepCG option so that cache tables in the active database are duplicated as cache tables in the standby database, because the standby database is connected with the Oracle database.

In the following example:

- The -from option specifies the file name prefix of the active database's checkpoint and transaction log files.

- The -host option specifies the host name of the TimesTen system where the active database resides.

- The -uid and -pwd options specify a user name and password of a TimesTen internal user defined in the active database that has been granted the ADMIN privilege.

- The -cacheuid and -cachepwd options specify the cache administration user name and password.

- cachestandby is the DSN of the standby database.

% ttRepAdmin -duplicate -from cacheact -host "sys3" -uid cacheuser -pwd timesten
-cacheuid cacheuser -cachepwd oracle -keepCG cachestandby

Start the ttIsql utility and connect to the cachestandby DSN as the cache manager user. Set the cache administration user name and password by calling the ttCacheUidPwdSet built-in procedure.

% ttIsql "DSN=cachestandby;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheUidPwdSet('cacheuser','oracle');

The ttGrid cache grid was created from the first standalone TimesTen database. Since the grid already exists, it does not need to be created again.

The ttRepAdmin -duplicate -keepCG utility command associated the standby database to the ttGrid cache grid so this association does not need to be done explicitly.

If desired, you can test the connectivity between the standby database and the Oracle database using the instructions stated in "Testing the connectivity between the TimesTen and Oracle databases".

Start the cache agent on the standby database by calling the ttCacheStart built-in procedure as the cache manager user:

Command> CALL ttCacheStart;

As the cache manager user, start the replication agent on the standby database by calling the ttRepStart built-in procedure.

Command> CALL ttRepStart;

If any global cache groups were created, the database must attach to the cache grid that it is associated with in order to update the cache tables of the global cache groups. Attaching the database to the grid allows the database to become a member of the grid so that cache instances in the cache tables of the global cache groups can maintain consistency among the databases within the grid.

As the cache manager user, attach the standby database to the ttGrid cache grid that it is associated with by calling the ttGridAttach built-in procedure. The node number for a standby database is 2. Use the same TCP/IP ports specified for the cache agent of the active and standby databases that were specified when configuring the active database.

In the following example:

- cacheact is a name that uniquely identifies the active database grid node.

- cachestand is a name that uniquely identifies the standby database grid node.

- sys3 is the host name of the TimesTen system where the active database resides.

- sys4 is the host name of the TimesTen system where the standby database resides.

- 5003 is the TCP/IP port for the active database's cache agent process.

- 5004 is the TCP/IP port for the standby database's cache agent process.

Command> CALL ttGridAttach(2,'cacheact','sys3',5003,'cachestand','sys4',5004);
Command> exit

Create and configure the read-only subscriber database

The following is the definition of the rosubscriber DSN for the read-only subscriber database of the active standby pair:

[rosubscriber]
DataStore=/users/OracleCache/subscr
PermSize=64
DatabaseCharacterSet=WE8ISO8859P1

As the instance administrator, create the read-only subscriber database as a duplicate of the standby database by running a ttRepAdmin -duplicate utility command from the read-only subscriber database system. The instance administrator user name of the standby database instance and read-only subscriber database instance must be identical.

Use the -noKeepCG option so that cache tables in the standby database are duplicated as regular tables in the read-only subscriber database because the read-only subscriber database is not connected with the Oracle database. As a result, the read-only subscriber database is not associated with a cache grid.

In the following example:

- The -from option specifies the file name prefix of the standby database's checkpoint and transaction log files.

- The -host option specifies the host name of the TimesTen system where the standby database resides.

- The -uid and -pwd options specify a user name and password of a TimesTen internal user defined in the standby database that has been granted the ADMIN privilege.

- rosubscriber is the DSN of the read-only subscriber database.

% ttRepAdmin -duplicate -from cachestand -host "sys4" -uid cacheuser -pwd timesten
-noKeepCG rosubscriber

As the cache manager user, start the replication agent on the read-only subscriber database by calling the ttRepStart built-in procedure.

% ttIsql "DSN=rosubscriber;UID=cacheuser;PWD=timesten"
Command> CALL ttRepStart;
Command> exit

Example of data sharing among the grid members

The definition of the oratt.subscriber cached Oracle Database table is shown in "Global cache groups".

The following is the data in the oratt.subscriber cached Oracle Database table.

SUBSCRIBERID  NAME              MINUTES_BALANCE   LAST_CALL_DURATION
------------  ----------------  ---------------   ------------------
1001  Jane Anderson                  75                   15
1004  Robert Phillips                60                   20
1005  William Ackerman               40                   10
1009  Sandy Little                   90                   30

The oratt.subscriber TimesTen cache table in the subscriber_accounts global cache group is initially empty in all five TimesTen databases (cachealone1, cachealone2, cacheactive, cachestandby, rosubscriber):

Command> SELECT * FROM oratt.subscriber;
0 rows found.

Issue the following SELECT statement on the cachealone1 TimesTen database to dynamically load one cache instance from the cached Oracle Database table into the TimesTen cache table:

Command> SELECT * FROM oratt.subscriber WHERE subscriberid = 1004;
< 1004, Robert Phillips, 60, 20 >

As a result, the cachealone1 standalone database grid member has ownership of the cache instance with subscriber ID 1004. This cache instance does not exist in any of the other grid members.

Next, issue the following SELECT statement on the cachealone2 TimesTen database to dynamically load one cache instance from the cached Oracle Database table into the TimesTen cache table:

Command> SELECT * FROM oratt.subscriber WHERE subscriberid = 1004;
< 1004, Robert Phillips, 60, 20 >

As a result, the cachealone2 standalone database grid member has taken ownership of the cache instance with subscriber ID 1004 from the cachealone1 grid member. This cache instance no longer exists in cachealone1 and does not exist in any of the other grid members.

Next issue the following INSERT statement on the cacheactive TimesTen database to insert a new cache instance into the TimesTen cache table:

Command> INSERT INTO oratt.subscriber VALUES (1012, 'Charles Hill', 80, 16);

As a result, the cacheactive active database grid node has ownership of the cache instance with subscriber ID 1012. The cache instance is replicated to the cachestandby standby database and the rosubscriber read-only subscriber database. The cache instance does not exist in any of the other grid members. The insert operation is also automatically propagated to the oratt.subscriber cached Oracle Database table.

A standby database or a read-only subscriber database cannot directly take ownership of a cache instance. A dynamic or manual load operation is prohibited including SELECT statements that result in a dynamic load because these databases are read-only.

No data sharing occurs with cache tables in local cache groups among the grid members. Each grid member can have a different number of local cache groups. If two grid members have a local cache group with the same definition, the data in the cache table within one grid member can overlap with the data in the cache table within the other grid member. There is no concept of cache instance ownership for cache tables in local cache groups.

Performing global queries on a cache grid

If you want to access data on all the nodes of a cache grid, perform a global query. For example, consider this statement:

SELECT MAX(salary) FROM employees;

When global query processing is not enabled, the statement returns the maximum salary for the rows that exist on the local node. When global query processing is enabled, it returns the maximum salary across all employee records in the cache grid.

A global query can reference a cache table or a noncache table in all attached grid members. The referenced tables can be any combination of local tables, cache tables, views, materialized views and table synonyms. The tables must have the same definition for columns affected by the global query.

Enable global query processing by setting an optimizer flag. Before executing a global query, turn autocommit off and call the ttOptSetFlag built-in procedure to set the GlobalProcessing optimizer flag to 1:

autocommit 0;
CALL ttOptSetFlag('GlobalProcessing', 1);

You can perform global queries with local joins by using the GlobalLocalJoin optimizer flag instead of the GlobalProcessing optimizer flag. See "Performing global queries with local joins".

Global queries that are enabled by the GlobalProcessing optimizer flag have these restrictions:

- The query must reference exactly one table.

- The query cannot include a self join, a derived table or subqueries.

- The query cannot reference a global temporary table.

- The query cannot be performed on the standby database of an active standby grid member.

- ROWNUM and GROUP BY clauses cannot be used in the same query.

- The query cannot be used with GROUPING SETS, CUBE, ROLLUP, GROUPING, GROUPING_ID, or GROUP_ID.

- The query cannot include the WITH clause.

- The query cannot include analytic SQL functions.

- The PassThrough connection attribute must be set to 0.

Performing global queries with local joins

You can execute a global query with a local join. This means that the SELECT statement is global (selects across grid members), but the join result is local (the join resides on the local node). You may find it useful to join fact and dimension tables, to join tables that are a similar size and whose data are distributed based on the join key or to join tables of a global cache group based on a primary key or foreign key relationship. Use the GlobalLocalJoin optimizer flag to enable a global query with local join.

Global queries with local joins can join cache tables, global cache tables, noncache tables with the same definition, views and materialized views. Global queries with local joins can include sequences.

A global query executed in serializable isolation belongs to the global transaction of the SELECT statement. A global query executed in read committed isolation is executed in its own transaction on the remote nodes.

These operations in a global query are executed locally in each grid member:

- Joins

- Derived tables

- Views

- GROUP BY, HAVING, ORDER BY and DISTINCT clauses in a subquery

These operations in the main query of a global query are executed globally:

- GROUP BY clause and aggregation.

- ORDER BY clause.

- DISTINCT clause.

- HAVING clause. This clause cannot contain a join.

Synonyms are resolved on the node where the query originates.

Before executing a global query with local join, turn autocommit off and call the ttOptSetFlag built-in procedure to set the GlobalLocalJoin optimizer flag to 1:

autocommit off;
CALL ttOptSetFlag('GlobalLocalJoin', 1)

Global queries with local joins have these restrictions:

- The query cannot include the ROWNUM expression.

- The query cannot include a set operator.

- The query cannot include the WITH clause.

- The query cannot be used with GROUPING SETS, CUBE, ROLLUP, GROUPING, GROUPING_ID, or GROUP_ID.

- The query cannot include analytic SQL functions.

- The PassThrough connection attribute must be set to 0.

- The query cannot be performed on the standby database of an active standby grid member.

Obtaining information about the location of data in the cache grid

You may wish to execute a global query without changing the location of the data.You can use SQL functions to determine which grid node contains the information and then execute a query for the information from that node.

Use these SQL functions in a global query to obtain information about the location of data in the cache grid:

- TTGRIDMEMBERID() - Returns the node ID of the node on which the query is executed.

- TTGRIDNODENAME() - Returns the name of the node on which the query is executed.

- TTGRIDUSERASSIGNEDNAME() - Returns the user-assigned name of the node on which the query is executed. The user assigns the name when the ttGridAttach built-in procedure is called. If you are using Oracle Clusterware, you do not call ttGridAttach directly and the user-assigned name is generated by TimesTen.

These functions can be used in a SELECT statement and in these clauses of a SELECT statement:

- WHERE clause

- GROUP BY clause

- ORDER BY clause

Figure 6-1 shows a cache grid whose members have user-assigned names alone1, alone2, and an active standby pair on nodes cacheact and cachestand. Queries do not retrieve data from the standby database. The standby database has the same data as the active database.

Figure 6-1 Location of data in a cache grid

The following example shows a global query that retrieves employee_id, the user-assigned node name, and the member ID from the employee table from the grid members.

autocommit off;
CALL ttOptSetFlag('GlobalProcessing', 1);
SELECT employee_id, TTGRIDUSERASSIGNEDNAME(), TTGRIDMEMBERID() FROM employees;
COMMIT;
< 100, alone1, 1>
< 101, alone2, 2>
< 102, cacheact, 3>
< 103, alone1, 1>
< 104, cacheact, 3>
...

The rows that are returned show which grid node and member owns each row of the cache instance. Subsequent queries can access the appropriate node without changing the ownership of the data. For example, execute this query on grid member cacheact, including TTGRIDUSERASSIGNEDNAME() in the query to verify that cacheact is the grid where the query is executed:

SELECT employee_id, last_name, hire_date , TTGRIDUSERASSIGNEDNAME()
FROM employees
WHERE employee_id=104;
< 104, Ernst, 1991-05-21 00:00:00, cacheact >

For more information about TTGRIDMEMBERID(), TTGRIDNODENAME() and TTGRIDUSERASSIGNEDNAME(), see "Cache grid functions" in Oracle TimesTen In-Memory Database SQL Reference.

Adding other elements to a cache grid or grid member

If a database that contains a global cache group is attached to a cache grid, a subsequent database can attach to the same grid and become a grid member only if it contains a global cache group with the same definition as the global cache group in the database that is attached to the grid. The subsequent database cannot attach to the same grid if it contains more or fewer global cache groups than the database that is attached to the grid. Each database can contain a different number of local cache groups with non-matching definitions between the databases.

Before you can create a new dynamic AWT global cache group in a TimesTen database that is attached to a cache grid, stop the replication agent on the database. Then restart the replication agent after creating the global cache group. The new global cache group cannot be manually or dynamically loaded, and its cache tables cannot be updated until the cache group has been created with the same definition in all the grid members. In the standalone databases and the active database, create the new global cache group manually. For the standby database and the read-only subscriber databases, use the ttDestroy utility to drop the databases and a ttRepAdmin -duplicate utility command to re-create the databases so that they contain the new global cache group.

7 Managing a Caching Environment

The following sections describe how to manage and monitor various aspects of a caching system such as cache grids, cache groups, and the cache agent process:

- Checking the status of the cache and replication agents

- Monitoring cache groups and cache grids

- Managing a caching environment with Oracle Database objects

- Impact of failed autorefresh operations on TimesTen databases

- Dropping Oracle Database objects used by autorefresh cache groups

- Monitoring the cache administration user's tablespace

- Recovering after failure of a grid node

- Backing up and restoring a database with cache groups

- Changing cache user names and passwords

Checking the status of the cache and replication agents

You can use either the ttAdmin or ttStatus utility to check whether the TimesTen cache agent and replication agent processes are running as well as determine each agent's start policy.

Example 7-1 Using ttAdmin to determine the cache and replication agents status

You can use a ttAdmin -query utility command to determine whether the cache and replication agents are running, and the cache and replication agent start policies for a TimesTen database:

% ttAdmin -query cachealone1
RAM Residence Policy            : inUse
Replication Agent Policy        : manual
Replication Manually Started    : True
Cache Agent Policy              : always
Cache Agent Manually Started    : True

For more information about the ttAdmin utility, see "ttAdmin" in Oracle TimesTen In-Memory Database Reference.

Example 7-2 Using ttStatus to determine the cache and replication agents status

You can use the ttStatus utility to determine whether the cache and replication agents are running, and the cache and replication agent start policies for all TimesTen databases in the installed instance:

% ttStatus
TimesTen status report as of Thu May  7 13:42:01 2009

Daemon pid 9818 port 4173 instance myinst
TimesTen server pid 9826 started on port 4175
------------------------------------------------------------------------
Data store /users/OracleCache/alone1
There are 38 connections to the data store
Shared Memory KEY 0x02011c82 ID 895844354
PL/SQL Memory KEY 0x03011c82 ID 895877123 Address 0x10000000
Type            PID     Context     Connection Name              ConnID
Cache Agent     1019    0x0828f840  Handler                           2
Cache Agent     1019    0x083a3d40  Timer                             3
Cache Agent     1019    0x0842d820  Aging                             4
Cache Agent     1019    0x08664fd8  Garbage Collector(-1580741728)    5
Cache Agent     1019    0x084d6ef8  Marker(-1580213344)               6
Cache Agent     1019    0xa5bb8058  DeadDsMonitor(-1579684960)        7
Cache Agent     1019    0x088b49a0  CacheGridEnv                     14
Cache Agent     1019    0x0896b9d0  CacheGridSend                    15
Cache Agent     1019    0x089fb020  CacheGridSend                    16
Cache Agent     1019    0x08a619f8  CacheGridSend                    17
Cache Agent     1019    0x08ace538  CacheGridRec                     18
Cache Agent     1019    0x08b42e88  CacheGridRec                     19
Cache Agent     1019    0x08bb77d8  CacheGridRec                     20
Cache Agent     1019    0x08c2c128  CacheGridRec                     21
Cache Agent     1019    0x08ca0a78  CacheGridRec                     22
Cache Agent     1019    0x08d153c8  CacheGridRec                     23
Cache Agent     1019    0x08d89d18  CacheGridRec                     24
Cache Agent     1019    0x08dfe668  CacheGridRec                     25
Cache Agent     1019    0x08e72fb8  CacheGridRec                     26
Cache Agent     1019    0x08ee8020  CacheGridRec                     27
Cache Agent     1019    0x08f5d088  CacheGridRec                     28
Cache Agent     1019    0x08fd23f8  CacheGridRec                     29
Cache Agent     1019    0x09047768  CacheGridRec                     30
Replication     18051   0x08c3d900  RECEIVER                          8
Replication     18051   0x08b53298  REPHOLD                           9
Replication     18051   0x08af8138  REPLISTENER                      10
Replication     18051   0x08a82f20  LOGFORCE                         11
Replication     18051   0x08bce660  TRANSMITTER                      12
Subdaemon       9822    0x080a2180  Manager                        2032
Subdaemon       9822    0x080ff260  Rollback                       2033
Subdaemon       9822    0x08548c38  Flusher                        2034
Subdaemon       9822    0x085e3b00  Monitor                        2035
Subdaemon       9822    0x0828fc10  Deadlock Detector              2036
Subdaemon       9822    0x082ead70  Checkpoint                     2037
Subdaemon       9822    0x08345ed0  Aging                          2038
Subdaemon       9822    0x083a1030  Log Marker                     2039
Subdaemon       9822    0x083fc190  AsyncMV                        2040
Subdaemon       9822    0x084572f0  HistGC                         2041
Replication policy  : Manual
Replication agent is running.
Cache Agent policy  : Always
TimesTen's Cache agent is running for this data store
PL/SQL enabled.
------------------------------------------------------------------------

The information displayed by the ttStatus utility include the following that pertains to TimesTen Cache for each TimesTen database in the installed instance:

- The names of the cache agent process threads that are connected to the TimesTen database

- The names of the replication agent process threads that are connected to the TimesTen database

- Status on whether the cache agent is running

- Status on whether the replication agent is running

- The cache agent start policy

- The replication agent start policy

For more information about the ttStatus utility, see "ttStatus" in Oracle TimesTen In-Memory Database Reference.

Cache agent and replication connections

When a connection from the cache agent to the Oracle database fails, the cache agent attempts to connect every 10 seconds. If the cache agent cannot connect to the Oracle database, the cache agent restarts after 10 minutes. This behavior repeats forever.

When a connection from the replication agent to the Oracle database fails, the replication agent attempts to reconnect to the Oracle database after 120 seconds. If it cannot reconnect after 120 seconds, the replication agent stops and does not restart.

If Fast Application Notification (FAN) is enabled on the Oracle database, the cache agent and the replication agent receive immediate notification of connection failures. If FAN is not enabled, the agents may wait until a TCP timeout occurs before becoming aware that the connection has failed.

If the Oracle Real Application Clusters (Oracle RAC) is enable on the Oracle database, along with FAN and Transparent Application Failover (TAF), then TAF manages the connection to a new Oracle Database instance. See Chapter 11, "Using TimesTen Application-Tier Database Cache in an Oracle RAC Environment".

Monitoring cache groups and cache grids

The following sections describe how to obtain information about cache grids and cache groups, and how to monitor the status of cache group operations:

- Using the ttIsql utility's cachegroups command

- Monitoring autorefresh operations on cache groups

- Monitoring AWT cache groups

- Obtaining information for a cache grid

- Tracking DDL statements issued on cached Oracle Database tables

Using the ttIsql utility's cachegroups command

You can obtain information about cache groups in a TimesTen database using the ttIsql utility's cachegroups command.

Example 7-3 ttIsql utility's cachegroups command

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> cachegroups;

Cache Group CACHEUSER.RECENT_SHIPPED_ORDERS:

Cache Group Type: Read Only
Autorefresh: Yes
Autorefresh Mode: Incremental
Autorefresh State: On
Autorefresh Interval: 1440 Minutes
Autorefresh Status: ok
Aging: Timestamp based uses column WHEN_SHIPPED lifetime 30 days cycle 24 hours on

Root Table: ORATT.ORDERS
Table Type: Read Only

Cache Group CACHEUSER.SUBSCRIBER_ACCOUNTS:

Cache Group Type: Asynchronous Writethrough global (Dynamic)
Autorefresh: No
Aging: LRU on

Root Table: ORATT.SUBSCRIBER
Table Type: Propagate

Cache Group CACHEUSER.WESTERN_CUSTOMERS:

Cache Group Type: User Managed
Autorefresh: No
Aging: No aging defined

Root Table: ORATT.ACTIVE_CUSTOMER
Where Clause: (oratt.active_customer.region = 'West')
Table Type: Propagate

Child Table: ORATT.ORDERTAB
Table Type: Propagate

Child Table: ORATT.ORDERDETAILS
Where Clause: (oratt.orderdetails.quantity >= 5)
Table Type: Not Propagate

Child Table: ORATT.CUST_INTERESTS
Table Type: Read Only

3 cache groups found.

The information displayed by the ttIsql utility's cachegroups command include:

- Cache group type, including whether the cache group is dynamic or global

- Autorefresh attributes (mode, state, interval) and status, if applicable

- Aging policy, if applicable

- Name of root table and, if applicable, name of child tables

- Cache table WHERE clause, if applicable

- Cache table attributes (read-only, propagate, not propagate)

For more information about the ttIsql utility's cachegroups command, see "ttIsql" in Oracle TimesTen In-Memory Database Reference.

Monitoring autorefresh operations on cache groups

TimesTen offers several mechanisms to obtain information and statistics about autorefresh operations on cache groups. See "Monitoring autorefresh cache groups" in Oracle TimesTen In-Memory Database Troubleshooting Guide.

Monitoring AWT cache groups

TimesTen offers several mechanisms to obtain information and statistics about operations in AWT cache groups. See "AWT performance monitoring" in Oracle TimesTen In-Memory Database Troubleshooting Guide.

Configuring a transaction log file threshold for AWT cache groups

The replication agent uses the transaction log to determine which updates on cache tables in AWT cache groups have been propagated to the cached Oracle Database tables and which updates have not. If updates are not being automatically propagated to the Oracle database because of a failure, transaction log files accumulate on disk. Examples of a failure that prevents propagation are that the replication agent is not running or the Oracle database server is unavailable. For more information about accumulation of transaction log files, see "Monitoring accumulation of transaction log files" in Oracle TimesTen In-Memory Database Operations Guide.

You can call the ttCacheAWTThresholdSet built-in procedure as the cache manager user to set a threshold for the number of transaction log files that can accumulate before TimesTen stops tracking updates on cache tables in AWT cache groups. The default threshold is 0. This built-in procedure can only be called if the TimesTen database contains AWT cache groups.

After the threshold has been exceeded, you need to manually synchronize the cache tables with the cached Oracle Database tables using an UNLOAD CACHE GROUP statement followed by a LOAD CACHE GROUP statement. TimesTen may purge transaction log files even if they contain updates that have not been propagated to the cached Oracle Database tables.

Example 7-4 Setting a transaction log file threshold for AWT cache groups

In this example, if the number of transaction log files that contain updates on cache tables in AWT cache groups exceeds 5, TimesTen stops tracking updates and can then purge transaction log files that may contain unpropagated updates:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheAWTThresholdSet(5);

You can call the ttCacheAWTThresholdGet built-in procedure to determine the current transaction log file threshold setting:

Command> CALL ttCacheAWTThresholdGet;
< 5 >
Command> exit

Obtaining information for a cache grid

You can use the following mechanisms to display information on any cache grid and their grid members:

- Call the ttGridInfo built-in procedure as the cache manager user to return the grid name, cache administration user name, operating system platform, and TimesTen major release number for a specified cache grid or all existing cache grids:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttGridInfo('ttGrid');
< TTGRID, CACHEUSER, Linux Intel x86, 32-bit, 11, 2, 1 >

For more information about the ttGridInfo built-in procedure, see "ttGridInfo" in Oracle TimesTen In-Memory Database Reference.

- Call the ttGridNodeStatus built-in procedure as the cache manager user to return the grid name, member ID, node number, indication of whether the node is attached to the grid, host name, node name, IP address, and cache agent TCP/IP port number for all members of a specified cache grid or all existing cache grids:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttGridNodeStatus;
< TTGRID, 1, 1, T, sys1, TTGRID_alone1_1, 140.87.0.201, 5001, <NULL>, <NULL>,
<NULL>, <NULL>, <NULL> >
< TTGRID, 2, 1, T, sys2, TTGRID_alone2_2, 140.87.0.202, 5002, <NULL>, <NULL>,
<NULL>, <NULL>, <NULL> >
< TTGRID, 3, 1, T, sys3, TTGRID_cacheact_3A, 140.87.0.203, 5003, T, sys4,
TTGRID_cachestand_3B, 140.87.0.204, 5004 >

For more information about the ttGridNodeStatus built-in procedure, see "ttGridNodeStatus" in Oracle TimesTen In-Memory Database Reference.

Suspending global AWT cache group operations

You can use the ttGridGlobalCGSuspend built-in procedure to temporarily block these operations for global AWT cache groups:

- Dynamic loading

- Deleting cache instances

Use the ttGridGlobalCGResume built-in procedure to re-enable these operations.

Tracking DDL statements issued on cached Oracle Database tables

When a DDL statement is issued on a cached Oracle Database table, this statement can be tracked in the Oracle Database TT_version_DDL_L table when the Oracle Database TT_version_schema-ID_DDL_T trigger is fired to insert a row into the table, where version is an internal TimesTen version number and schema-ID is the ID of user that owns the cached Oracle Database table. A trigger is created for each Oracle Database user that owns cached Oracle Database tables. One DDL tracking table is created to store DDL statements issued on any cached Oracle Database table. The cache administration user owns the TT_version_DDL_L table and the TT_version_schema-ID_DDL_T trigger.

To enable tracking of DDL statements issued on cached Oracle Database tables, call the ttCacheDDLTrackingConfig built-in procedure as the cache manager user. By default, DDL statements are not tracked.

For more information about the ttCacheDDLTrackingConfig built-in procedure, see "ttCacheDDLTrackingConfig" in Oracle TimesTen In-Memory Database Reference.

Example 7-5 Enabling tracking of DDL statements issued on cached Oracle Database tables

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheDDLTrackingConfig('enable');

The TT_version_DDL_L table and TT_version_schema-ID_DDL_T trigger are automatically created if the cache administration user has been granted the set of required privileges including RESOURCE and CREATE ANY TRIGGER. These Oracle Database objects are created when you create a cache group after tracking of DDL statements has been enabled.

If you manually created the Oracle Database objects used to manage the caching of Oracle Database data, you need to run the ttIsql utility's cachesqlget command with the ORACLE_DDL_TRACKING option and the INSTALL flag as the cache manager user. This command should be run for each Oracle Database user that owns cached Oracle Database tables that you want to track DDL statements on. Running this command generates a SQL*Plus script used to create the TT_version_DDL_L table and TT_version_schema-ID_DDL_T trigger in the Oracle database.

After generating the script, use SQL*Plus to run the script as the sys user.

Example 7-6 Creating DDL tracking table and trigger when Oracle Database objects were manually created

In this example, the SQL*Plus script generated by the ttIsql utility's cachesqlget command is saved to the /tmp/trackddl.sql file. The owner of the cached Oracle Database table oratt is passed as an argument to the command.

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> cachesqlget ORACLE_DDL_TRACKING oratt INSTALL /tmp/trackddl.sql;
Command> exit

% sqlplus sys as sysdba
Enter password: password
SQL> @/tmp/trackddl
SQL> exit

When you need to issue DDL statements such as CREATE, DROP or ALTER on cached Oracle Database tables in order to make changes to the Oracle Database schema, drop the affected cache groups before you modify the Oracle Database schema. Otherwise operations such as autorefresh may fail. You do not need to drop cache groups if you are altering the Oracle Database table to add a column. To issue other DDL statements for Oracle Database tables, first perform the following tasks:

1. Use DROP CACHE GROUP statements to drop all cache groups that cache the affected Oracle Database tables. If you are dropping an AWT cache group, use the ttRepSubscriberWait built-in procedure to make sure that all committed updates on the cache tables have been propagated to the cached Oracle Database tables before the cache group is dropped.

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttRepSubscriberWait('_AWTREPSCHEME','TTREP','_ORACLE','sys1',-1);

2. Stop the cache agent.

3. Make the desired changes to the Oracle Database schema.

4. Use CREATE CACHE GROUP statements to re-create the cache groups, if feasible.

If you want to truncate an Oracle Database table that is cached in an autorefresh cache group, perform the following tasks:

1. Use an ALTER CACHE GROUP statement to set the cache group's autorefresh state to PAUSED.

2. Truncate the Oracle Database table.

3. Manually refresh the cache group using a REFRESH CACHE GROUP statement without a WHERE or WITH ID clause.

Autorefresh operations resume after you refresh the cache group.

You can run the TimesTen_install_dir/oraclescripts/cacheInfo.sql SQL*Plus script as the cache administration user to display information about the Oracle Database objects used to track DDL statements issued on cached Oracle Database tables:

% cd TimesTen_install_dir/oraclescripts
% sqlplus cacheuser/oracle
SQL> @cacheInfo
*************DDL Tracking Object Information  ***************
Common DDL Log Table Name: TT_05_DDL_L
DDL Trigger Name: TT_05_315_DDL_T
Schema for which DDL Trigger is tracking: ORATT
Number of cache groups using the DDL Trigger: 10
****************************

The information returned for each Oracle Database user that owns cached Oracle Database tables includes the name of the DDL tracking table, the name of its corresponding DDL trigger, the name of the user that the DDL trigger is associated with, and the number of cache groups that cache a table owned by the user associated with the DDL trigger.

If a particular table is cached in more than one grid member, each grid member contributes to the cache group count. An active standby pair counts as one grid member. If a cache group contains more than one cache table, each cache table owned by the user associated with the DDL trigger contributes to the cache group count.

Managing a caching environment with Oracle Database objects

For an autorefresh cache group, TimesTen creates a change log table and trigger in the Oracle database for each cache table in the cache group. The trigger is fired for each committed insert, update, or delete operation on the cached Oracle Database table. The trigger records the primary key of the updated rows in the change log table. The cache agent periodically scans the change log table for updated keys and then joins this table with the cached Oracle Database table to get a snapshot of the latest updates.

Note:
If you are caching the same Oracle table in more than one TimesTen database, see "Caching the same Oracle table on two or more TimesTen databases" for performance considerations.

The Oracle Database objects used to process autorefresh writethrough operations can be automatically created by TimesTen as described in "Automatically create Oracle Database objects used to manage data caching" when you create a cache group with the AUTOREFRESH MODE INCREMENTAL cache group attribute. Alternatively, you can manually create these objects as described in "Manually create Oracle Database objects used to manage data caching" before performing any cache grid or cache group operation if, for security purposes, you do not want to grant the RESOURCE and CREATE ANY TRIGGER privileges to the cache administration user required to automatically create these objects.

Before the Oracle Database objects can be automatically or manually created, you must:

- Create a cache administration user in the Oracle database as described in "Create the Oracle database users".

- Set the cache administration user name and password in the TimesTen database as described in "Set the cache administration user name and password".

- Start the cache agent as described in "Managing the cache agent".

For each cache administration user, TimesTen creates the following Oracle Database tables, where version is an internal TimesTen version number and object-ID is the ID of the cached Oracle Database table:

Table Name

Description

TT_version_AGENT_STATUS

Created when the first cache group is created. Stores information about each Oracle Database table cached in an autorefresh cache group.

TT_version_AR_PARAMS

Created when the cache administration user name and password is set. Stores the action to take when the cache administration user's tablespace is full.

TT_version_CACHE_STATS

Created when the cache administration user name and password is set.

TT_version_DATABASES

Created when the cache administration user name and password is set. Stores the autorefresh status for all TimesTen databases that cache data from the Oracle database.

TT_version_DB_PARAMS

Created when the cache administration user name and password is set. Stores the cache agent timeout, recovery method for dead cache groups, and the cache administration user's tablespace usage threshold.

TT_version_DBSPECIFIC_PARAMS

Internal use.

TT_version_DDL_L

Created when the cache administration user name and password is set. Tracks DDL statements issued on cached Oracle Database tables.

TT_version_DDL_TRACKING

Created when the cache administration user name and password is set. Stores a flag indicating whether tracking of DDL statements on cached Oracle Database tables is enabled or disabled.

TT_version_REPACTIVESTANDBY

Created when the first AWT cache group is created. Tracks the state and roles of TimesTen databases containing cache tables in an AWT cache group that are replicated in an active standby pair replication scheme.

TT_version_REPPEERS

Created when the first AWT cache group is created. Tracks the time and commit sequence number of the last update on the cache tables that was asynchronously propagated to the cached Oracle Database tables.

TT_version_SYNC_OBJS

Created when the first cache group is created.

TT_version_USER_COUNT

Created when the first cache group is created. Stores information about each cached Oracle Database table.

TT_version_object-ID_L

One change log table is created per Oracle Database table cached in an autorefresh cache group when the cache group is created. Tracks updates on the cached Oracle Database table.

For each cache administration user, TimesTen creates the following Oracle Database triggers, where version is an internal TimesTen version number, object-ID is the ID of the cached Oracle Database table, and schema-ID is the ID of user who owns the cached Oracle Database table:

Trigger Name

Description

TT_version_REPACTIVESTANDBY_T

Created when the first AWT cache group is created. When fired, inserts rows into the TT_version_REPACTIVESTANDBY table.

TT_version_object-ID_T

One trigger is created per Oracle Database table cached in an autorefresh cache group when the cache group is created. Fired for each insert, delete or update operation issued on the cached Oracle Database table to track operations in the TT_version_object-ID_L change log table.

TT_version_schema-ID_DDL_T

One trigger for each user who owns cached Oracle Database tables. Created when a cache group is created after tracking of DDL statements has been enabled. Fired for each DDL statement issued on a cached Oracle Database table to track operations in the TT_version_DDL_L table.

For the timesten user, TimesTen creates the following Oracle Database tables:

Table Name

Description

TT_GRIDID

Created by running the SQL*Plus script initCacheGlobalSchema.sql. Stores the ID number assigned to the most recently created cache grid.

TT_GRIDINFO

Created by running the SQL*Plus script initCacheGlobalSchema.sql. Stores the grid name, grid ID, and name of the cache administration user for all existing cache grids.

For each cache administration user, TimesTen creates the following Oracle Database tables, where version is an internal TimesTen version number and grid-ID is the ID number of the cache grid:

Table Name

Description

TT_version_grid-name_grid-IDCGNODEID

One table is created per cache grid when a grid is created. Stores the operating system name and version, and TimesTen release number.

TT_version_grid-name_grid-IDCGNODEINFO

One table is created per cache grid when a grid is created. Stores the host name, member name, IP address, and cache agent TCP/IP port of all attached grid members.

TT_version_grid-name_grid-IDCGGROUPDEFS

One table is created per cache grid when a grid is created. Stores the cache group name, owner, reference count and SQL text of all global cache groups in standalone TimesTen databases or active standby pairs that are associated with the cache grid.

Impact of failed autorefresh operations on TimesTen databases

A change log table is created in the cache administration user's tablespace for each Oracle Database table that is cached in an autorefresh cache group. For each update operation issued on these cached Oracle Database tables, a row is inserted into their change log table to keep track of updates that need to be applied to the TimesTen cache tables upon the next incremental autorefresh cycle. TimesTen periodically deletes rows in the change log tables that have been applied to the cache tables.

An Oracle Database table cannot be cached in more than one cache group within a TimesTen database. However, an Oracle Database table can be cached in more than one TimesTen database. This results in an Oracle Database table corresponding to multiple TimesTen cache tables. If updates on cached Oracle Database tables are not being automatically refreshed into all of their corresponding cache tables because the cache agent is not running on one or more of the TimesTen databases that the Oracle Database tables are cached in, rows in their change log tables are not deleted by default. The cache agent may not be running on a particular TimesTen database because the agent was explicitly stopped or never started, the database was destroyed, or the installed instance that the database resides in is down. As a result, rows accumulate in the change log tables and degrade the performance of autorefresh operations on cache tables in TimesTen databases where the cache agent is running. This can also cause the cache administration user's tablespace to fill up.

You can set a cache agent timeout to prevent rows from accumulating in the change log tables and not being deleted. The following criteria must be met in order for TimesTen to delete rows in the change log tables when the cache agent is not running on a TimesTen database and a cache agent timeout is set:

- Oracle Database tables are cached in autorefresh cache groups within more than one TimesTen database.

- The cache agent is running on at least one of the TimesTen databases but is not running on at least another database.

- Rows in the change log tables have been applied to the cache tables on all TimesTen databases where the cache agent is running.

- For those databases where the cache agent is not running, the agent process has been down for a period of time that exceeds the cache agent timeout.

Call the ttCacheConfig built-in procedure as the cache manager user from any of the TimesTen databases that cache data from the Oracle database. Pass the AgentTimeout string to the Param parameter and the timeout setting as a numeric string to the Value parameter. Do not pass in any values to the tblOwner and tblName parameters as they are not applicable to setting a cache agent timeout.

Example 7-7 Setting a cache agent timeout

In the following example, the cache agent timeout is set to 900 seconds (15 minutes):

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheConfig('AgentTimeout',,,'900');

To determine the current cache agent timeout setting, call ttCacheConfig passing only the AgentTimeout string to the Param parameter:

Command> CALL ttCacheConfig('AgentTimeout');
< AgentTimeout, <NULL>, <NULL>, 900 >

The default cache agent timeout is 0 seconds which means rows in the change log tables are not deleted until they have been applied to all its cache tables. If you set the cache agent timeout to a value between 1 and 600 seconds, the timeout is set to 600 seconds. The cache agent timeout applies to all TimesTen databases that cache data from the same Oracle database and have the same cache administration user name setting.

When determining a proper cache agent timeout setting, consider the time it takes to load the TimesTen database into memory, the time to start the cache agent process, potential duration of network outages, and anticipated duration of planned maintenance activities.

Each TimesTen database, and all of its autorefresh cache groups have an autorefresh status to determine whether any deleted rows from the change log tables were not applied to the cache tables in the cache groups. If rows were deleted from the change log tables and not applied to some cache tables because the cache agent on the database was down for a period of time that exceeded the cache agent timeout, those cache tables are no longer synchronized with the cached Oracle Database tables. Subsequent updates on the cached Oracle Database tables are not automatically refreshed into the cache tables until the accompanying cache group is recovered.

The following are the possible statuses for an autorefresh cache group:

- ok: All of the deleted rows from the change log tables were applied to its cache tables. Incremental autorefresh operations continue to occur on the cache group.

- dead: Some of the deleted rows from the change log tables were not applied to its cache tables so the cache tables are not synchronized with the cached Oracle Database tables. Autorefresh operations have ceased on the cache group and do not resume until the cache group has been recovered.

- recovering: The cache group is being recovered. Once recovery completes, the cache tables are synchronized with the cached Oracle Database tables, the cache group's autorefresh status is set to ok, and incremental autorefresh operations resume on the cache group.

The following are the possible autorefresh statuses for a TimesTen database:

- alive: All of its autorefresh cache groups have an autorefresh status of OK.

- dead: All of its autorefresh cache groups have an autorefresh status of dead.

- recovering: At least one of its autorefresh cache groups have an autorefresh status of recovering.

If the cache agent on a TimesTen database is down for a period of time that exceeds the cache agent timeout, the autorefresh status of the database is set to dead. Also, the autorefresh status of all autorefresh cache groups within that database are set to dead.

If you have enabled SNMP traps, a trap is thrown when the autorefresh status of a database is set to dead.

Call the ttCacheDbCgStatus built-in procedure as the cache manager user to determine the autorefresh status of a cache group and its accompanying TimesTen database. Pass the owner of the cache group to the cgOwner parameter and the name of the cache group to the cgName parameter.

Example 7-8 Determining the autorefresh status of a cache group and TimesTen database

In the following example, the autorefresh status of the database is alive and the autorefresh status of the cacheuser.customer_orders read-only cache group is ok:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheDbCgStatus('cacheuser','customer_orders');
< alive, ok >

To view only the autorefresh status of the database and not of a particular cache group, call ttCacheDbCgStatus without any parameters:

Command> CALL ttCacheDbCgStatus;
< dead, <NULL> >

If the autorefresh status of a cache group is ok, its cache tables are being automatically refreshed based on its autorefresh interval. If the autorefresh status of a database is alive, the autorefresh status of all its autorefresh cache groups are ok.

If the autorefresh status of a cache group is dead, its cache tables are no longer being automatically refreshed when updates are committed on the cached Oracle Database tables. The cache group must be recovered in order to resynchronize the cache tables with the cached Oracle Database tables.

You can configure a recovery method for cache groups whose autorefresh status is dead.

Call the ttCacheConfig built-in procedure as the cache manager user from any of the TimesTen databases that cache data from the Oracle database. Pass the DeadDbRecovery string to the Param parameter and the recovery method as a string to the Value parameter. Do not pass in any values to the tblOwner and tblName parameters as they are not applicable to setting a recovery method for dead cache groups.

The following are the valid recovery methods:

- Normal: When the cache agent starts, a full autorefresh operation is performed on cache groups whose autorefresh status is dead in order to recover those cache groups. This is the default recovery method.

- Manual: For each explicitly loaded cache group whose autorefresh status is dead, a REFRESH CACHE GROUP statement must be issued in order to recover these cache groups after the cache agent starts.
For each dynamic cache group whose autorefresh status is dead, a REFRESH CACHE GROUP or UNLOAD CACHE GROUP statement must be issued in order to recover these cache groups after the cache agent starts.

- None: Cache groups whose autorefresh status is dead must be dropped and then re-created after the cache agent starts in order to recover them.

Example 7-9 Configuring the recovery method for dead cache groups

In the following example, the recovery method is set to Manual for cache groups whose autorefresh status is dead:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheConfig('DeadDbRecovery',,,'Manual');

To determine the current recovery method for dead cache groups, call ttCacheConfig passing only the DeadDbRecovery string to the Param parameter:

Command> CALL ttCacheConfig('DeadDbRecovery');
< DeadDbRecovery, <NULL>, <NULL>, manual >

The recovery method applies to all autorefresh cache groups in all TimesTen databases that cache data from the same Oracle database and have the same cache administration user name setting.

If you have enabled SNMP traps, a trap is thrown when the cache agent starts and the recovery method is set to Manual or None to alert you to manually issue a statement such as REFRESH CACHE GROUP or DROP CACHE GROUP in order to recover cache groups in the database whose autorefresh status is dead.

When a cache group begins the recovery process, its autorefresh status is changed from dead to recovering, and the status of the accompanying TimesTen database is changed to recovering, if it is currently dead.

After the cache group has been recovered, its autorefresh status is changed from recovering to ok. Once all cache groups have been recovered and their autorefresh statuses are ok, the status of the accompanying TimesTen database is changed from recovering to alive.

A full autorefresh operation requires more system resources to process than an incremental autorefresh operation when there is a small volume of updates to refresh and a large number of rows in the cache tables. If you need to bring a TimesTen database down for maintenance activities and the volume of updates anticipated during the downtime on the Oracle Database tables that are cached in autorefresh cache groups is small, you can consider temporarily setting the cache agent timeout to 0. When the database is brought back up and the cache agent restarted, incremental autorefresh operations resumes on cache tables in autorefresh cache groups. Full autorefresh operations are avoided because the autorefresh status on the accompanying cache groups were not changed from ok to dead so those cache groups do not need to go through the recovery process. Make sure to set the cache agent timeout back to its original value once the database is back up and the cache agent has been started.

Dropping Oracle Database objects used by autorefresh cache groups

If a TimesTen database that contains autorefresh cache groups becomes unavailable, Oracle Database objects such as change log tables and triggers used to implement autorefresh operations continue to exist in the Oracle database. A TimesTen database is unavailable, for example, when the TimesTen system is taken offline or the database has been destroyed without dropping its autorefresh cache groups.

Oracle Database objects used to implement autorefresh operations also continue to exist in the Oracle database when a TimesTen database is no longer being used but still contains autorefresh cache groups. Rows continue to accumulate in the change log tables. This impacts autorefresh performance on other TimesTen databases. Therefore, it is desirable to drop these Oracle Database objects associated with the unavailable or abandoned TimesTen database.

Run the TimesTen_install_dir/oraclescripts/cacheCleanUp.sql SQL*Plus script as the cache administration user to drop the Oracle Database objects used to implement autorefresh operations. The host name of the TimesTen system and the TimesTen database path name are passed as arguments to the cacheCleanUp.sql script. You can run the cacheInfo.sql script as the cache administration user to determine the host name of the TimesTen system and the database path name. The cacheInfo.sql script can also be used to determine whether any objects used to implement autorefresh operations exist in the Oracle database.

Example 7-10 Dropping Oracle Database objects for autorefresh cache groups

In the following example, the TimesTen database still contained one read-only cache group customer_orders with cache tables oratt.customer and oratt.orders when the database was dropped. The cacheCleanUp.sql script drops the change log tables and triggers associated with the two cache tables.

% cd TimesTen_install_dir/oraclescripts
% sqlplus cacheuser/oracle
SQL> @cacheCleanUp "sys1" "/users/OracleCache/alone1"

*****************************OUTPUT**************************************
Performing cleanup for object_id: 69959 which belongs to table : CUSTOMER
Executing: delete from tt_05_agent_status where host = sys1 and datastore =
/users/OracleCache/alone1 and object_id = 69959
Executing: drop table tt_05_69959_L
Executing: drop trigger tt_05_69959_T
Executing: delete from tt_05_user_count where object_id = object_id1
Performing cleanup for object_id: 69966 which belongs to table : ORDERS
Executing: delete from tt_05_agent_status where host = sys1 and datastore =
/users/OracleCache/alone1 and object_id = 69966
Executing: drop table tt_05_69966_L
Executing: drop trigger tt_05_69966_T
Executing: delete from tt_05_user_count where object_id = object_id1
**************************************************************************

Monitoring the cache administration user's tablespace

The following sections describe how to manage the cache administration user's tablespace:

- Defragmenting change log tables in the tablespace

- Receiving notification on tablespace usage

- Recovering from a full tablespace

Defragmenting change log tables in the tablespace

Prolonged use or a heavy workload of the change log tables for autorefresh cache groups can result in fragmentation of the tablespace. In order to prevent degradation of the tablespace from fragmentation of the change log tables, TimesTen calculates the percentage of fragmentation for the change log tables as a ratio of used space to the total size of the space. If this ratio falls below a defined threshold, TimesTen alerts you of the necessity for defragmentation of the change log tables by logging a message and, if you have enabled SNMP traps, by throwing the ttCacheAutorefreshLogSpaceDeFragDetectedTrap SNMP trap. By default, this threshold is set to 40%. You can configure what the fragmentation threshold should be with the ttCacheConfig built-in procedure.

Note:
Messages are logged to the user and support error logs. For details, see "Modifying informational messages" in the Oracle TimesTen In-Memory Database Operations Guide.

To set the fragmentation threshold, call the ttCacheConfig built-in procedure as the cache manager user from any of the TimesTen databases that cache data from the Oracle database. Pass the AutoRefreshLogFragmentationWarningPCT string to the Param parameter and the threshold setting as a numeric string to the Value parameter.

Note:
Do not pass in any values to the tblOwner and tblName parameters as they are not applicable to setting the fragmentation threshold.

Example 7-11 Setting a fragmentation threshold

In the following example, the fragmentation threshold is set to 50%:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheConfig('AutoRefreshLogFragmentationWarningPCT',,,'50');
< AutoRefreshLogFragmentationWarningPCT, <NULL>, <NULL>, 50 >
1 row found.

To determine the current fragmentation threshold setting, call ttCacheConfig passing the AutoRefreshLogFragmentationWarningPCT string to the Param parameter:

Command> CALL ttCacheConfig('AutoRefreshLogFragmentationWarningPCT');
< AutoRefreshLogFragmentationWarningPCT, <NULL>, <NULL>, 50 >

You can either configure TimesTen to perform defragmentation automatically or manually initiate defragmentation. To configure what action is taken when the ratio falls below the fragmentation threshold, call the ttCacheConfig built-in procedure with the AutoRefreshLogDeFragmentAction string to the Param parameter and the desired action as the Value parameter as follows:

Note:
Do not pass in any values to the tblOwner and tblName parameters as they are not applicable to setting the defragmentation action.

- Manual. This is the default. No action is taken to defragment the change log tables. Any defragmentation must be performed manually by executing the ttCacheAutoRefreshLogDeFrag built-in procedure. See "Manually defragmenting the change log tables for autorefresh cache groups" for more information.

- Compact: TimesTen defragments the change log tables.

- CompactAndReclaim: TimesTen defragments the change log tables and reclaims the space.

Note:
When reclaiming space, the change log table is briefly locked, which temporarily suspends writing into the base table.

Example 7-12 Configuring action for fragmentation

In the following example, the action is set to CompactAndReclaim so that when the fragmentation ratio falls below the threshold, TimesTen defragments the change log tables and reclaims the space:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheConfig('AutoRefreshLogDeFragmentAction',,,'CompactAndReclaim');
< AutoRefreshLogDeFragmentAction, <NULL>, <NULL>, compactandreclaim >
1 row found.

To determine the current fragmentation threshold setting, call ttCacheConfig passing the AutoRefreshLogDeFragmentAction string to the Param parameter:

Command> CALL ttCacheConfig('AutoRefreshLogDeFragmentAction');
< AutoRefreshLogDeFragmentAction , <NULL>, <NULL>, compactandreclaim >

You can discover the fragmentation percentage of the tablespace and when the last defragmentation operation was performed with the following returned columns from the ttCacheAutorefreshStatsGet built-in procedure:

- AutoRefreshLogFragmentationPCT: The current fragmentation percentage for the tablespace.

- AutoRefreshLogFragmentationTS: The timestamp of when the last fragmentation percentage was calculated.

- autorefLogDeFragCnt: The count for how many times the tables in this particular cache group have been defragmented.

For more details, see "ttCacheAutorefreshStatsGet" in the Oracle TimesTen In-Memory Database Reference.

Manually defragmenting the change log tables for autorefresh cache groups

To manually initiate a defragmentation of the change log tables, call the ttCacheAutoRefreshLogDeFrag built-in procedure as the cache manager user from any of the TimesTen databases that cache data from the Oracle database. Pass in one of the following strings as the parameter:

- Compact: Defragment the change log tables.

- CompactAndReclaim: Defragment the change log tables and reclaim the space.

Note:
When reclaiming space, the change log table is briefly locked, which temporarily suspends writing into the base table.

Example 7-13 Manually defragmenting the change log tables

In the following example, the user calls the ttCacheAutoRefreshLogDeFrag built-in procedure with the CompactAndReclaim option:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheAutoRefreshLogDeFrag('CompactAndReclaim');

Receiving notification on tablespace usage

In order to avoid the tablespace becoming full, you can configure TimesTen to return a warning to the application when an update operation such as an UPDATE, INSERT or DELETE statement is issued on cached Oracle Database tables and causes the usage of the cache administration user's tablespace to exceed a specified threshold.

Call the ttCacheConfig built-in procedure as the cache manager user from any of the TimesTen databases that cache tables from the Oracle database. Pass the AutoRefreshLogTblSpaceUsagePCT string to the Param parameter and the threshold as a numeric string to the Value parameter. The threshold value represents the percentage of space used in the cache administration user's tablespace upon which a warning is returned to the application when an update operation is issued on a cached Oracle Database table. Do not pass in any values to the tblOwner and tblName parameters as they are not applicable to setting a warning threshold for the usage of the cache administration user's tablespace.

The cache administration user must be granted the SELECT privilege on the Oracle Database SYS.DBA_DATA_FILES table in order for the cache manager user to set a warning threshold on the cache administration user's tablespace usage, and for the cache administration user to monitor its tablespace to determine if the configured threshold has been exceeded.

Example 7-14 Setting a cache administration user's tablespace usage warning threshold

The following example configures a warning to be returned to the application that issues an update operation on a cached Oracle Database table if it results in the usage of the cache administration user's tablespace to exceed 80 percent:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheConfig('AutoRefreshLogTblSpaceUsagePCT',,,'80');

To determine the current cache administration user's tablespace usage warning threshold, call ttCacheConfig passing only the AutoRefreshLogTblSpaceUsagePCT string to the Param parameter:

Command> CALL ttCacheConfig('AutoRefreshLogTblSpaceUsagePCT');
< AutoRefreshLogTblSpaceUsagePCT, <NULL>, <NULL>, 80 >

The default cache administration user's tablespace usage warning threshold is 0 percent which means that no warning is returned to the application regardless of the tablespace usage. The cache administration user's tablespace usage warning threshold applies to all TimesTen databases that cache tables from the same Oracle database and have the same cache administration user name setting.

If you have enabled SNMP traps, a trap is thrown when the cache administration user's tablespace usage has exceeded the configured threshold.

Recovering from a full tablespace

By default, when the cache administration user's tablespace is full, an error is returned to the Oracle Database application when it attempts a DML operation, such as an UPDATE, INSERT or DELETE statement, on a particular cached Oracle Database table.

Rather than TimesTen returning an error to the Oracle Database application when the cache administration user's tablespace is full, you can configure TimesTen to delete existing rows from the change log tables to make space for new rows when an update operation is issued on a particular cached Oracle Database table. If some of the deleted change log table rows have not been applied to the TimesTen cache tables, a full autorefresh operation is performed on those cache tables in each TimesTen database that contains the tables upon the next autorefresh cycle.

Call the ttCacheConfig built-in procedure as the cache manager user from any of the TimesTen databases that cache tables from the Oracle database. Pass the TblSpaceFullRecovery string to the Param parameter, the owner and name of the cached Oracle Database table to the tblOwner and tblName parameters, respectively, on which you want to configure an action to take if the cache administration user's tablespace becomes full, and the action itself as a string to the Value parameter.

The following are the valid actions:

- None: Return an Oracle Database error to the application when an update operation is issued on the cached Oracle Database table. This is the default action.

- Reload: Delete rows from the change log table and perform a full autorefresh operation on the cache table upon the next autorefresh cycle when an update operation is issued on the cached Oracle Database table.

Example 7-15 Configuring an action when the cache administration user's tablespace becomes full

In the following example, rows are deleted from the change log table and a full autorefresh operation is performed on the cache table upon the next autorefresh cycle when an update operation is issued on the oratt.customer cached Oracle Database table while the cache administration user's tablespace is full:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttCacheConfig('TblSpaceFullRecovery','oratt','customer','Reload');

To determine the current action to take when an update operation is issued on a particular cached Oracle Database table if the cache administration user's tablespace is full, call ttCacheConfig passing only the TblSpaceFullRecovery string to the Param parameter, and the owner and name of the cached Oracle Database table to the tblOwner and tblName parameters, respectively:

Command> CALL ttCacheConfig('TblSpaceFullRecovery','oratt','customer');
< TblSpaceFullRecovery, ORATT, CUSTOMER, reload >

The action to take when update operations are issued on a cached Oracle Database table while the cache administration user's tablespace is full applies to all TimesTen databases that cache tables from the same Oracle database and have the same cache administration user name setting,

If you have enabled SNMP traps, a trap is thrown when an update operation is issued on a cached Oracle Database table and the cache administration user's tablespace is full.

Recovering after failure of a grid node

When a standalone database grid member fails, the cache agent automatically restarts if the cache agent start policy is manual or always. The grid member is automatically reattached to the grid when the database recovers. If the cache agent start policy is norestart, you must restart the cache agent and then call the ttGridAttach built-in procedure to reattach the member to the grid. See "Set a cache agent start policy".

You can verify that a standalone database grid member is attached to the grid by calling the ttRepStateGet built-in procedure. If it is attached, you should see this output:

Command> CALL ttRepStateGet;
< IDLE, AVAILABLE >
1 row found.

If the active or the standby database node in an active standby pair grid member fails when Oracle Clusterware is managing the nodes in the grid, the grid node is automatically reattached to the grid when the cache agent restarts. For more information about how Oracle Clusterware handles failures, see "Recovering from failures" in Oracle TimesTen In-Memory Database Replication Guide.

If the active standby pair grid member is not managed by Oracle Clusterware, then perform the steps in "Recovering from a failure of the active database" or "Recovering from a failure of the standby database" in Oracle TimesTen In-Memory Database Replication Guide. If the cache agent start policy is manual or always, the grid node is automatically reattached to the grid after the database recovers.). If the cache agent start policy is norestart, call the ttGridAttach built-in procedure to reattach the member to the grid.

Call the ttRepStateGet built-in procedure from the active database to verify that the active database is available and that the active standby pair is attached to the grid:

Command> CALL ttRepStateGet;
< ACTIVE, AVAILABLE >
1 row found.

For more information, see "ttRepStateGet" in Oracle TimesTen In-Memory Database Reference.

A multinode failure can occur because of a hardware failure or network failure, for example. After a multinode failure occurs, call the ttGridAttach built-in procedure for each member that needs to be reattached. The operation fails for each grid member until you call the built-in procedure on the last grid member to be reattached. Call ttGridAttach again for the grid members that have not yet been attached and the operation succeeds. This sequence is necessary to prevent a "split-brain" situation with grid members being unaware of each other's states.

Backing up and restoring a database with cache groups

Databases containing cache groups can be backed up and restored with either the ttBackup or ttMigrate utilities.

- If the restored database connects to the same backend Oracle database, then use the ttBackup and ttRestore utilities, then drop and recreate all cache groups in the restored TimesTen database. If they are static cache groups, you may be required to reload them. For dynamic cache groups, the reload is optional as data is pulled in from the Oracle database as it is referenced.

Note:
If another TimesTen database is used to connect to the original backend Oracle database (and now no longer connects) and if all cache groups in the TimesTen database were not cleanly dropped, then execute the cacheCleanUp.sql SQL*Plus script against the original Oracle database to remove all leftover objects. Specify the host and path for the original TimesTen database.

- If the restored database connects to a different backend Oracle database than what it had originally connected with, then perform one of the following:

- Backing up and restoring using the ttBackup and ttRestore utilities

- Backing up and restoring with the ttMigrate utility

Backing up and restoring using the ttBackup and ttRestore utilities

When you use the ttBackup utility, it backs up the TimesTen database with all of its data at a particular time. Thus, if you want to use these cache groups again, restoring this backup requires additional action as the restored data within the cache groups are out of date and out of sync with the data in the backend Oracle database.

Note:
See "Migration, Backup, and Restoration" in the Oracle TimesTen In-Memory Database Installation Guide and "ttBackup" and "ttRestore" in the Oracle TimesTen In-Memory Database Reference for more information on these tools.

If the restored database connects to a different backend Oracle database than what it had originally connected with and you want to use the ttBackup and ttRestore utilities to backup and restore your database, then perform the following:

1. Execute the ttBackup utility command to backup the database and its objects into a binary file. For example, to backup the cachealone1 database using the /tmp/dump directory for temporary storage:

$ ttBackup -dir /tmp/dump -connstr "DSN=cachealone1"

2. Drop all cache groups and destroy the database. Since the database still exists with its cache groups, drop the cache groups and then destroy the database before restoring in the same or another location.

$ ttIsql -connstr "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> call ttCacheStop;
Command> DROP CACHE GROUP readcache;
Command> exit;
Disconnecting...
Done.

$ ttDestroy cachealone1

3. Restore the database with the ttRestore utility and then delete the temporary directory.

$ ttRestore -dir /tmp/dump -connstr "DSN=cachealone1"
Restore started ...
Restore complete

$ rm -r /tmp/dump

4. In order to re-synchronize the data within the cache groups, you must drop and recreate the cache groups:

1. Connect to the TimesTen database.

2. Drop the cache groups that were restored with the ttRestore utility. Because the data is out of sync, you may see errors.

3. Specify the cache administrator user name and password with the ttCacheUidPwdSet built-in procedure.

4. Start the cache agent.

5. Recreate and, if required, reload the cache groups.

$ ttIsql -connstr "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"

Command> DROP CACHE GROUP readcache;
Command> call ttCacheUidPwdSet('cacheuser','oracle');
Command> call ttCacheStart;
Command> CREATE READONLY CACHE GROUP readcache
> AUTOREFRESH INTERVAL 5 SECONDS
> FROM oratt.readtab
> (keyval NUMBER NOT NULL PRIMARY KEY, str VARCHAR2(32));
Command> LOAD CACHE GROUP readcache COMMIT EVERY 256 ROWS;
2 cache instances affected.

Note:
If the restored TimesTen database is not able to connect to any backend Oracle database, then TimesTen cannot autorefresh the data for the read-only cache groups.

Backing up and restoring with the ttMigrate utility

The ttMigrate utility saves tables and indexes from a TimesTen database into a binary file. When a cache group is migrated and included in the binary file, it includes the cache group definition and schema; however, the data of the cache group is not migrated.

Note:
See "Migration, Backup, and Restoration" in the Oracle TimesTen In-Memory Database Installation Guide and "ttMigrate" in the Oracle TimesTen In-Memory Database Reference for more information on these tools.

If the restored database connects to a different backend Oracle database than what it had originally connected with and you want to use the ttMigrate utility for backing up and restoring the database, then perform the following:

1. Execute the ttMigrate -c utility command to save the database and its objects into a binary file.

$ ttMigrate -c "DSN=cachealone1" cachealone1.ttm
...
Saving user CACHEUSER
User successfully saved.

Saving user ORATT
User successfully saved.

Saving table CACHEUSER.READTAB
Saving rows...
2/2 rows saved.
Table successfully saved.

Saving cache group CACHEUSER.READCACHE
Saving cached table ORATT.READTAB
Cache group successfully saved.

2. Drop all cache groups and destroy the TimesTen database:

1. Stop the cache agent.

2. Drop all cache groups. You may see errors reported, which can be ignored. When you drop all cache groups before destroying the TimesTen database, all metadata on the Oracle Database for these cache groups is deleted.

3. Destroy the TimesTen database.

Command> call ttCacheStop;
Command> DROP CACHE GROUP readcache;
Command> exit
Disconnecting...
Done.
$ ttDestroy cachealone1

3. Create and restore the database:

1. Create the TimesTen database with a first connection request.

2. Create the TimesTen cache table user and the TimesTen cache manager user. Grant appropriate privileges to these users.

Note:
Depending on which TimesTen release you are migrating from, the users and privileges may or may not be migrated. See "ttMigrate" in the Oracle TimesTen In-Memory Database Reference for more information.

3. Restore the database from the saved binary file with the ttMigrate -r utility command.

$ ttIsql cachealone1
Command> CREATE USER cacheuser IDENTIFIED BY timesten;
User created.

Command> GRANT CREATE SESSION, CACHE_MANAGER, CREATE ANY TABLE TO cacheuser;
Command> CREATE USER oratt IDENTIFIED BY timesten;
User created.

Command> exit
Disconnecting...
Done.

$ ttMigrate -r -relaxedUpgrade -cacheuid cacheuser -cachepwd oracle
-connstr "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
cachealone1.ttm
...
Restoring table CACHEUSER.READTAB
Restoring rows...
2/2 rows restored.
Table successfully restored.

Restoring cache group CACHEUSER.READCACHE
Restoring cached table ORATT.READTAB
1/1 cached table restored.
Cache group successfully restored.

4. Connect to the restored database and reset the cache autorefresh state:

1. Connect to the TimesTen database with ttIsql.

2. Specify the cache administrator user name and password with the ttCacheUidPwdSet built-in procedure.

3. Start the cache agent.

4. Alter the cache groups to set autorefresh state to ON.

$ ttIsql -connstr "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> call ttCacheUidPwdSet('cacheuser','oracle');
Command> call ttCacheStart;
Command> ALTER CACHE GROUP readcache SET AUTOREFRESH STATE ON;

Note:
If the restored TimesTen database is not able to connect to any backend Oracle database, then TimesTen cannot autorefresh the data for the read-only cache groups.

Changing cache user names and passwords

Perform the following to change any of the user names or passwords for the TimesTen cache manager user, its companion Oracle user, or the cache administration user:

1. If you want to modify the cache manager user or password, perform the following:

Note:
Passwords for both the TimesTen cache manager user and its companion Oracle user can be changed at any time.
The name for the cache manager user on TimesTen must be the same as its companion Oracle user; however, the passwords may be different. For more details on the cache manager user and its companion Oracle user, see "Create the TimesTen users".

1. On the TimesTen database, if you want to modify the password of the cache manager user, then use the ALTER USER statement on the active master.

Command> ALTER USER cacheuser IDENTIFIED BY newpwd;

2. On the back-end Oracle database, you can modify the cache manager companion Oracle password with the ALTER USER statement. If you are working on TimesTen, you can use Passthrough 3 to execute this directly on the Oracle database.

Command> passthrough 3;
Command> ALTER USER cacheuser IDENTIFIED BY newpwd;

Note:
If you have modified the password for the companion Oracle user, reconnect to the TimesTen database as the cache manager user providing passwords for the cache manager user and its companion Oracle user.

3. If you want to change the cache manager user, you must first drop all cache groups that the cache manager user owns before dropping the existing user and creating a new user.

Note:
Alternatively, if you want to use a different user as the cache manager user, ensure that it has the correct privileges and a companion Oracle user with the correct privileges.

In addition, since the cache manager user must have a companion Oracle user with the same name, you must either:

- Drop all tables owned by the current companion Oracle user, drop the user, and then re-create it with the same name as the new cache manager user. If the current companion Oracle user is the cache administration user, see Step 3.

- Choose another Oracle user that has the same name as the cache manager user and provides the same functionality.

For full details on how to create a cache manager user and its companion Oracle user, see "Create the TimesTen users".

4. If the TimesTen cache manager user name or password are defined in the sys.odbc.ini (or odbc.ini) file, update the new cache manager user name or password in the sys.odbc.ini (or odbc.ini) file on both the active and standby masters.

2. If you want to modify the cache administration user or its password, perform the following:

1. On the back-end Oracle database, you can modify the cache administration password with the ALTER USER statement. The password of the cache administration user can be changed at any time.
If you are working on TimesTen, you can use Passthrough 3 to execute this directly on the Oracle database.

Command> passthrough 3;
Command> ALTER USER cacheuser IDENTIFIED BY newpwd;

2. If you want to change the cache administration user, you must first drop all cache groups on the TimesTen database that the cache administration user manages before you can drop the cache administration user on the Oracle database and create a new user. Dropping the cache groups on TimesTen removes all metadata associated with those cache groups.
When you create a new cache administration user on the Oracle database, you must follow the same instructions for creating a cache adminstration user that are provided in the "Create the Oracle database users".

3. Set the new user name or password for the cache administration user by executing the ttCacheUidPwdSet built-in procedure on the active master database.

Note:
See "Set the cache administration user name and password".

Command> call ttCacheUidPwdSet('cacheuser','newpwd');

8 Cache Performance

The following sections contain information about cache performance.

Note:

See Oracle TimesTen In-Memory Database Troubleshooting Guide for extensive information about monitoring autorefresh operations and improving autorefresh performance. See "Monitoring autorefresh cache groups" and "Poor autorefresh performance".

Oracle TimesTen In-Memory Database Troubleshooting Guide also has information about AWT cache group performance. See "Monitoring AWT performance" and "Possible causes of poor AWT performance".

- Dynamic load performance

- Improving AWT throughput

- Improving performance when using incremental autorefresh for read-only cache groups

- Improving performance when reclaiming memory during autorefresh operations

- Retrieving statistics on autorefresh transactions

- Caching the same Oracle table on two or more TimesTen databases

Dynamic load performance

Dynamic loading based on a primary key search of the root table has faster performance than primary key searches on a child table or foreign key searches on a child table. For more details, see "Dynamically loading a cache instance".

Improving AWT throughput

Use the following methods to improve through put for AWT cache groups:

- Improving AWT throughput with parallel propagation

- Improving AWT throughput with SQL array execution

Improving AWT throughput with parallel propagation

To improve throughput for an AWT cache group, you can configure multiple threads that act in parallel to propagate and apply transactional changes to the Oracle database. Parallel propagation enforces transactional dependencies and applies changes in AWT cache tables to Oracle Database tables in commit order. For full details, see "Configuring parallel propagation to Oracle Database tables".

Improving AWT throughput with SQL array execution

By default, an AWT cache group uses the PL/SQL execution method to apply changes within TimesTen to the Oracle database. AWT bundles all pending operations into a single PL/SQL collection that is sent to the Oracle database server to be executed. This execution method is appropriate when there are mixed transactions and network latency between TimesTen and the Oracle database server.

Use the CacheAWTMethod first connection attribute to specify SQL array execution to apply changes within TimesTen to the Oracle database. This method is appropriate when the same type of operation is repeated. For example, SQL array execution is very efficient when a user does an update that affects several rows of the table. Updates are grouped together and sent to the Oracle database server in one batch.

The PL/SQL execution method transparently falls back to SQL array execution mode temporarily when it encounters one of the following:

- A statement that is over 32761 bytes in length.

- A statement that references a column of type BINARY FLOAT, BINARY DOUBLE and VARCHAR/VARBINARY of length greater than 4000 bytes.

Note:
You can also set this value with the ttDBConfig built-in procedure with the CacheAwtMethod parameter. For details, see "ttDBConfig" in the Oracle TimesTen In-Memory Database Reference.

For more information, see "CacheAWTMethod" in Oracle TimesTen In-Memory Database Reference.

Improving performance when using incremental autorefresh for read-only cache groups

The following sections describe how to improve performance when you either have large transactions or join large tables when using incremental autorefresh for read-only cache groups:

- Improving execution of large transactions when using incremental autorefresh for read-only cache groups

- Configuring a select limit when using incremental autorefresh for read-only cache groups

Improving execution of large transactions when using incremental autorefresh for read-only cache groups

At certain times, you may execute large transactions, such as for the end of the month, the end of a quarter, or the end of the year transactions. You may also have situations where you modify or add a large amount of data in the Oracle database over a short period of time. For incremental autorefresh, read-only cache groups, TimesTen could potentially run out of permanent space when an autorefresh operation applies either one of these cases. Therefore, for these situations, you can configure an autorefresh transaction limit, where the large amount of data is broken up, applied, and committed over several smaller transactions.

The ttCacheAutorefreshXactLimit built-in procedure enables you to direct autorefresh to commit after executing a specific number of operations. This option applies to all incremental autorefresh read-only cache groups that are configured with the same autorefresh interval.

Since the single transaction is broken up into several smaller transactions, transactional consistency cannot be maintained while autorefresh is in progress. Once the autorefresh cycle completes, the data is transactionally consistent. To protect instance consistency, we recommend that you set the autorefresh transaction limit only on cache groups with only a single table, since instance consistency between the parent and child tables is not guaranteed. When the autorefresh transaction limit is turned on, TimesTen does not enforce the foreign key relationship that protects instance consistency. Once you turn off the autorefresh transaction limit for incremental autorefresh read-only cache groups, both instance and transactional consistency are maintained again.

Note:
If you are using an active standby pair, you must call the ttCacheAutorefreshXactLimit built-in procedure for the same values on both the active and standby masters.

Using ttCacheAutorefreshXactLimit

Note:
For more information, such as the syntax and the returned result set, see "ttCacheAutorefreshXactLimit" in the Oracle TimesTen In-Memory Database Replication Guide.

For the month end processing, there can be a large number updates in a single transaction for the Oracle tables that are cached in autorefresh cache groups. In order to ensure that the large transaction does not fill up permanent memory, you can enable autorefresh to commit after every 256 (or any other user specified number) operations with the ttCacheAutorefreshXactLimit built-in procedure.

Turn on an autorefresh transaction limit for incremental autorefresh read-only cache groups before a large transaction with the ttCacheAutorefreshXactLimit built-in procedure where the value is set to ON or to a specific number of operations. Then, when autorefresh finishes updating the cached tables in TimesTen, turn off the autorefresh transaction limit for incremental autorefresh read-only cache groups with the ttCacheAutorefreshXactLimit built-in procedure.

The following example sets up the transaction limit to commit after every 256 operations for all incremental autorefresh read-only cache groups that are defined with an interval value of 10 seconds.

call ttCacheAutorefreshXactLimit('10000', 'ON');

After the month end process has completed and the incremental autorefresh read-only cache groups are refreshed, disable the transaction limit for incremental autorefresh read-only cache groups that are defined with the interval value of 10 seconds.

call ttCacheAutorefreshXactLimit('10000', 'OFF');

To enable the transaction limit for incremental autorefresh read-only cache groups to commit after every 1024 operations, provide 1024 as the value as follows:

call ttCacheAutorefreshXactLimit('10000', '1024');

Example of potential transactional inconsistency

The following example uses the employee and departments table, where the department id of the department table is a foreign key that points to the department id of the employee table.

The following example creates two incremental autorefresh read-only cache groups, where each is in its own cache group. The autorefresh transaction limit is enabled with ttCacheAutorefreshXactLimit before a large transaction and is disabled after it completes.

1. Before you initiate the large transaction, invoke ttCacheAutorefreshXactLimit to set the interval value and the number of operations after which to automatically commit. The following sets the number of operations to three (which is intentionally low to show a brief example) for all incremental autorefresh read-only cache groups with a two second interval.

CALL ttCacheAutorefreshXactLimit('2000', '3');
< 2000, 3 >
1 row found.

2. Create the incremental autorefresh read-only cache groups with interval of two seconds. This example creates two static (non-dynamic) read-only cache groups, where each contains a single table.

CREATE READONLY CACHE GROUP cgDepts AUTOREFRESH MODE INCREMENTAL
INTERVAL 2 SECONDS
FROM departments
( department_id    NUMBER(4) PRIMARY KEY
, department_name  VARCHAR2(30) NOT NULL
, manager_id       NUMBER(6)
, location_id      NUMBER(4)
);

CREATE READONLY CACHE GROUP cgEmpls AUTOREFRESH MODE INCREMENTAL
INTERVAL 2 SECONDS
FROM employees
( employee_id    NUMBER(6) PRIMARY KEY
, first_name     VARCHAR2(20)
, last_name      VARCHAR2(25) NOT NULL
, email          VARCHAR2(25) NOT NULL UNIQUE
, phone_number   VARCHAR2(20)
, hire_date      DATE NOT NULL
, job_id         VARCHAR2(10) NOT NULL
, salary         NUMBER(8,2)
, commission_pct NUMBER(2,2)
, manager_id     NUMBER(6)
, department_id  NUMBER(4)
);

3. Perform a manual LOAD CACHE GROUP for both autorefresh cache groups.

LOAD CACHE GROUP cgDepts COMMIT EVERY 256 ROWS;
27 cache instances affected.

LOAD CACHE GROUP cgEmpls COMMIT EVERY 256 ROWS;
107 cache instances affected.

You can have inconsistency within the table during an autorefresh as shown with the employees table.

1. On TimesTen, select the minimum and maximum salary of all employees.

SELECT MIN(salary), MAX(salary) FROM employees;
< 2100, 24000 >
1 row found.

2. On the Oracle database, add 100,000 to everyone's salary.

UPDATE employees SET salary = salary + 100000;
107 rows updated.

3. On TimesTen, when you perform the SELECT again (while the autorefresh transactions are commmitted after every 3 records), it shows that while the maximum salary has updated, the minimum salary is still the old value.

SELECT MIN(salary), MAX(salary) FROM employees;
< 2100, 124000 >
1 row found.

4. However, once the autorefresh completes, transactional consistency is maintained. For this example, once the autorefresh process completes, all salaries have increased by 100,000.

SELECT MIN(salary), MAX(salary) FROM employees;
< 102100, 124000 >
1 row found.

5. The large transaction is complete, so disable the transaction limit for autorefresh cache groups with a 2 second interval.

call ttCacheAutorefreshXactLimit('2000', 'OFF');

You can have transactional inconsistency between cache groups if you perform a SQL statement while the autorefresh process is progressing. The following SELECT statement example executes against the employees and department table in the cgDepts autorefresh cache group. With this example, since the foreign key is not enforced on TimesTen and the autorefresh process applies several transactions, the employee table updates may be inserted before the department updates.

In addition, all of the updates for both tables in the cache group are not applied until the autorefresh cycle has completed. In the following example, the SELECT statement is executed before the autorefresh process is complete. Thus, the results do not show all of the expected data, such as the department name and several employees (some of the lawyers in the legal department 1000) are missing.

SELECT e.department_id, d.DEPARTMENT_NAME, e.FIRST_NAME, e.LAST_NAME
FROM employees e, departments d
WHERE e.DEPARTMENT_ID  = d.DEPARTMENT_ID (+)
AND e.department_id >= 1000 ORDER BY 1,2,3,4;
< 1000, <NULL>, Alan, Dershowitz >
< 1000, <NULL>, F. Lee, Bailey >
< 1000, <NULL>, Johnnie, Cochran >
3 rows found.

However, after the autorefresh process completes, transactional consistency is maintained. The following shows the same SELECT statement executed after the autorefresh is complete. All expected data, the department information and all of the new lawyers, are updated.

SELECT e.department_id, d.DEPARTMENT_NAME, e.FIRST_NAME, e.LAST_NAME
FROM employees e, departments d
WHERE e.DEPARTMENT_ID  = d.DEPARTMENT_ID (+)
AND e.department_id >= 1000 ORDER BY 1,2,3,4;
< 1000, Legal, Alan, Dershowitz >
< 1000, Legal, Barry, Scheck >
< 1000, Legal, F. Lee, Bailey >
< 1000, Legal, Johnnie, Cochran >
< 1000, Legal, Robert, Kardashian >
< 1000, Legal, Robert, Shapiro >
6 rows found.

For autorefresh cache groups that have more than one table, you can also experience transactional inconsistency if you execute SQL statements while the autorefresh process is in progress.

1. Initiate the transaction limit for incremental autorefresh cache groups of 2 seconds with the ttCacheAutorefreshXactLimit built-in procedure and create a single autorefresh cache group with two tables: the employees and departments tables.

CALL ttCacheAutorefreshXactLimit('2000', '3');
< 2000, 3 >
1 row found.

CREATE READONLY CACHE GROUP cgDeptEmpls AUTOREFRESH MODE INCREMENTAL
INTERVAL 2 SECONDS
FROM departments
( department_id    NUMBER(4) PRIMARY KEY
, department_name  VARCHAR2(30) NOT NULL
, manager_id       NUMBER(6)
, location_id      NUMBER(4)
)
, employees
( employee_id    NUMBER(6) PRIMARY KEY
, first_name     VARCHAR2(20)
, last_name      VARCHAR2(25) NOT NULL
, email          VARCHAR2(25) NOT NULL UNIQUE
, phone_number   VARCHAR2(20)
, hire_date      DATE NOT NULL
, job_id         VARCHAR2(10) NOT NULL
, salary         NUMBER(8,2)
, commission_pct NUMBER(2,2)
, manager_id     NUMBER(6)
, department_id  NUMBER(4)
, foreign key(department_id) references departments(department_id)
);

2. Manually load the cache group.

LOAD CACHE GROUP cgDeptEmpls COMMIT EVERY 256 ROWS;
27 cache instances affected.

3. Perform a SELECT statement on TimesTen that uploads all of the legal department data.

SELECT e.department_id, d.department_name, count(*)
FROM employees e, departments d
WHERE e.department_id  = d.department_id (+)
GROUP BY e.department_id, d.department_name
ORDER BY 1 desc;
< 110, Accounting, 2 >
< 100, Finance, 6 >
< 90, Executive, 3 >
< 80, Sales, 34 >
< 70, Public Relations, 1 >
< 60, IT, 5 >
< 50, Shipping, 45 >
< 40, Human Resources, 1 >
< 30, Purchasing, 6 >
< 20, Marketing, 2 >
< 10, Administration, 1 >
11 rows found.

4. On Oracle, insert a new legal department, numbered 1000, with 6 new lawyers in both the employee and department tables.

5. When performing a SELECT statement on TimesTen during the autorefresh process, only data on two of the lawyers in department 1000 have been uploaded into TimesTen.

SELECT e.department_id, d.department_name, count(*)
FROM employees e, departments d
WHERE e.department_id  = d.department_id (+)
GROUP BY e.department_id, d.department_name
ORDER BY 1 desc;
< 1000, Legal, 2 >
< 110, Accounting, 2 >
< 100, Finance, 6 >
< 90, Executive, 3 >
< 80, Sales, 34 >
< 70, Public Relations, 1 >
< 60, IT, 5 >
< 50, Shipping, 45 >
< 40, Human Resources, 1 >
< 30, Purchasing, 6 >
< 20, Marketing, 2 >
< 10, Administration, 1 >
12 rows found.

6. However, after the autorefresh process completes, all 6 employees (lawyers) in the legal department have been uploaded to TimesTen. Now, it is transactionally consistent.

SELECT e.department_id, d.department_name, COUNT(*)
FROM employees e, departments d
WHERE e.department_id  = d.department_id (+)
GROUP BY e.department_id, d.department_name
ORDER BY 1 desc;
< 1000, Legal, 6 >
< 110, Accounting, 2 >
< 100, Finance, 6 >
< 90, Executive, 3 >
< 80, Sales, 34 >
< 70, Public Relations, 1 >
< 60, IT, 5 >
< 50, Shipping, 45 >
< 40, Human Resources, 1 >
< 30, Purchasing, 6 >
< 20, Marketing, 2 >
< 10, Administration, 1 >
12 rows found.

7. The large transaction is complete, so disable the transaction limit for autorefresh cache groups with a 2 second interval.

call ttCacheAutorefreshXactLimit('2000', 'OFF');

Retrieving statistics to evaluate performance when a transaction limit is set

To see how a autorefresh transaction limit for a particular autorefresh interval is performing, you can retrieve statistics for the last 10 incremental autorefresh transactions for this autorefresh interval with the ttCacheAutorefIntervalStatsGet built-in procedure. See "Retrieving statistics on autorefresh transactions" for more information.

Configuring a select limit when using incremental autorefresh for read-only cache groups

To facilitate incremental autorefresh for read-only cache groups, TimesTen executes a table join query on both the Oracle database base table and its corresponding change log table to retrieve the incremental changes. However, if both tables are very large, the join query can be slow. In addition, if the Oracle database base table is continuously updated while the join-query is executing, you may receive the ORA-01555 “Snapshot too old” error from a long-running autorefresh query.

To avoid this situation, you can configure incremental autorefresh with a select limit, which joins the Oracle database base table with a limited number of rows from the autorefresh change log table. You can configure a select limit with the ttCacheAutorefreshSelectLimit built-in procedure.

Autorefresh continues to apply changes to the cached table incrementally until all the rows in the autorefresh change log table have been applied. When there are no rows left to apply, the autorefresh thread sleeps for the rest of the interval period.

Note:
For details on the syntax, parameters, result set, and restrictions, see "ttCacheAutorefreshSelectLimit" in the Oracle TimesTen In-Memory Database Reference.

For example, before a large transaction, you can call the ttCacheAutorefreshSelectLimit built-in procedure to set a select limit to 1000 rows for incremental autorefresh cache groups with an interval value of 10 seconds. The following example sets the value to ON.

Command> call ttCacheAutorefreshSelectLimit('10000', 'ON');
< 10000, ON >
1 row found.

The following example set a select limit to 2000 rows for incremental autorefresh cache groups with an interval value of 7 seconds.

Command> call ttCacheAutorefreshSelectLimit('7000', '2000');
< 7000, 2000 >
1 row found.

You can disable any select limit for incremental autorefresh cache groups with an interval value of 10 seconds by setting the value to OFF.

Command> call ttCacheAutorefreshSelectLimit('10000', 'OFF');
< 10000, OFF >
1 row found.

To see how a select limit for a particular autorefresh interval is performing, you can retrieve statistics for incremental autorefresh transactions for this autorefresh interval. See "Retrieving statistics on autorefresh transactions" for more information.

How to determine the cache group name for a particular select limit

To determine the interval for a cache group, use ttIsql and run the cachegroups command:

> cachegroups cgowner.cgname;

This returns all attributes for the cgowner.cgname cache group including the interval.

To determine which intervals have a select limit, you can run the following query on the Oracle database where <cacheAdminUser> is the cache administrator, <hostName> is the host name of the machine where the TimesTen database is located, <databaseFileName> is the database path taken from the DataStore attribute, and substitute the version number (such as 06) for the xx.

SELECT * FROM <cacheAdminUser>.tt_xx_arinterval_params
WHERE param='AutorefreshSelectEveryN'
AND host='<hostName>'
AND database like '%<databaseFileName>%'
ORDER BY arinterval;

For example, if the cache administrator user name is pat, the host name is myhost, the database file name is myTtDb, and 06 is substituted for xx that is the TimesTen minor release number then:

SELECT * FROM pat.tt_06_arinterval_params
WHERE param='AutorefreshSelectEveryN'
AND host='myhost'
AND database like '%myTtDb%'
ORDER BY arinterval;

The interval is stored in milliseconds.

Retrieving statistics to evaluate performance when using a select limit

To see how a select limit for a particular autorefresh interval is performing, you can retrieve statistics for incremental autorefresh transactions for this autorefresh interval with the ttCacheAutorefIntervalStatsGet built-in procedure. See "Retrieving statistics on autorefresh transactions" for more information.

Improving performance when reclaiming memory during autorefresh operations

As described "Transaction reclaim operations" in the Oracle TimesTen In-Memory Database Operations Guide, TimesTen resource cleanup occurs during the reclaim phase of a transaction commit. To improve performance, a number of transaction log records are cached in memory to reduce the need to access the transaction log on disk in the the commit buffer. However, TimesTen must access the transaction log on disk if the transaction is larger than the reclaim buffer.

When you are using autorefresh for your cache groups, the cache agent has its own reclaim buffer to manage the transactions that are committed within autorefresh operations. If the cache agent reclaim buffer is too small, the commit operations during autorefresh can take longer than expected as it must access the transaction log on disk. To avoid any performance issues, you can configure a larger reclaim buffer for the cache agent so that the cache agent can handle larger transactions in memory at reclaim time.

When using an active standy pair replication scheme to replicate autorefresh operations, the replication agent applies the same autorefresh operations as part of the replication. Thus, the replication agents on both the active and standby nodes have their own reclaim buffers that should be configured to be the same size or greater than the cache agent reclaim buffer.

The ttDbConfig built-in procedure provides the following parameters for setting the maximum size for the reclaim buffers for both the cache agent and the replication agent. (The memory for the reclaim buffers are allocated out of temporary memory.)

- CacheAgentCommitBufSize sets the maximum size for the reclaim buffer for the cache agent.

- RepAgentCommitBufSize sets the maximum size for the reclaim buffer for the replication agent. You should configure the maximum size for the reclaim buffer on both the active and standby nodes. It is recommended that you set the size for the reclaim buffers to the same value on both nodes, but not required.

Note:
For more details, see "ttDbConfig" in the Oracle TimesTen In-Memory Database Reference.

To determine if you should increment the size for the cache agent reclaim buffer, evaluate the CommitBufMaxReached and CommitBufNumOverflows statistics provided by the ttCacheAutorefIntervalStatsGet built-in procedure. For more details, see "Retrieving statistics on autorefresh transactions."

Retrieving statistics on autorefresh transactions

Call the ttCacheAutorefIntervalStatsGet built-in procedure for statistical information about the last 10 autorefresh cycles for a particular autorefresh interval defined for an incremental autorefresh read-only cache group.

Note:
For more information on syntax and the returned result set for this built-in procedure, see "ttCacheAutorefIntervalStatsGet" in the Oracle TimesTen In-Memory Database Reference.
This built-in procedure is useful if you have set an transaction limit or a select limit for incremental, autorefresh read-only cache groups. See "Improving execution of large transactions when using incremental autorefresh for read-only cache groups" and "Configuring a select limit when using incremental autorefresh for read-only cache groups" for details.

The following example shows how to call the ttCacheAutorefIntervalStatsGet built-in procedure to retrieve statistics for incremental autorefresh read-only cache groups that have been defined as static and have the interval of 2 seconds:

Command> call ttCacheAutorefIntervalStatsGet(2000, 1);

< 2000, 1, 21, 2013-04-30 06:05:38.000000, 100, 3761, 3761, 822, 1048576,
1280, 0, 58825, 63825, 13590, 0, 0, 0, 0, 0 >
< 2000, 1, 20, 2013-04-30 06:05:37.000000, 100, 85, 85, 18, 1048576, 1280,
0, 55064, 60064, 12768, 0, 0, 0, 0, 0 >
< 2000, 1, 19, 2013-04-30 06:05:32.000000, 100, 3043, 3043, 666, 1048576,
1280, 0, 54979, 59979, 12750, 0, 0, 0, 0, 0 >
< 2000, 1, 18, 2013-04-30 06:05:30.000000, 100, 344, 344, 74, 1048576,
1280, 0, 51936, 56936, 12084, 0, 0, 0, 0, 0 >
< 2000, 1, 17, 2013-04-30 06:05:28.000000, 100, 1826, 1826, 382, 1048576,
1280, 0, 51592, 56592, 12010, 0, 0, 0, 0, 0 >
< 2000, 1, 16, 2013-04-30 06:05:26.000000, 100, 55, 55, 12, 1048576,
1280, 0, 49766, 54766, 11628, 0, 0, 0, 0, 0 >
< 2000, 1, 15, 2013-04-30 06:05:22.000000, 100, 2901, 2901, 634, 1048576,
1280, 0, 49711, 54711, 11616, 0, 0, 0, 0, 0 >
< 2000, 1, 14, 2013-04-30 06:05:21.000000, 100, 55, 55, 12, 1048576,
1280, 0, 46810, 51810, 10982, 0, 0, 0, 0, 0 >
< 2000, 1, 13, 2013-04-30 06:05:10.000000, 100, 5844, 5844, 1263, 1048576,
1280, 0, 46755, 51755, 10970, 0, 0, 0, 0, 0 >
< 2000, 1, 12, 2013-04-30 06:05:08.000000, 100, 607, 607, 132, 1048576,
1280, 0, 40911, 45911, 9707, 0, 0, 0, 0, 0 >

10 rows found.

Caching the same Oracle table on two or more TimesTen databases

For each cache administration user, TimesTen creates a change log table and trigger (as part of what is created to manage caching) in the Oracle database for each cache table in the cache group. A trigger is fired for each committed insert, update, or delete operation on the cached Oracle Database table; the action is logged in the change log table.

If you cache the same Oracle database table in a cache group on two different TimesTen databases, we recommend that you use the same cache administration user name on both TimesTen databases as the owner of the cache table on each TimesTen database. When you use the same cache administration user, only one trigger and change log table are created to manage the changes to the base table. Thus, it is efficient and does not slow down the application.

If you create separate cache administration users on each TimesTen database to own the cache group that caches the same Oracle table, then separate triggers and change log tables exist on the Oracle database for the same table: one for each cache administration user. For example, if you have two separate TimesTen databases, each with their own cache administration user, two triggers fire for each DML operation on the base table, each of which are stored in a separate change log table. Firing two triggers and managing the separate change log tables can slow down the application.

The only reason to create separate cache administration users is if one of the TimesTen databases that caches the same table has a slow autorefresh rate or a slow connection to the Oracle database. In this case, having a single cache administration user on both TimesTen databases slows down the application on the faster connection, as it waits for the updates to be propagated to the slower database.

9 Cleaning up the Caching Environment

The following sections describe the various tasks that need to be performed in the TimesTen and Oracle databases to destroy a cache grid and drop cache groups. It also includes a recommendation for shutting down all components when using AWT cache groups.

- Detaching a TimesTen database from a cache grid

- Stopping the replication agent

- Dropping a cache group

- Destroying a cache grid

- Stopping the cache agent

- Destroying the TimesTen databases

- Dropping Oracle Database users and objects

- Recommended method for a scheduled shutdown of an active standby pair with AWT cache groups

Note:
If you are planning to use Oracle Clusterware to manage active standby pairs in a cache grid, see "Using Oracle Clusterware with a TimesTen cache grid" in Oracle TimesTen In-Memory Database Replication Guide.
Also see "Restricted commands and SQL statements" in Oracle TimesTen In-Memory Database Replication Guide. Use the ttCWAdmin utility to manage the active standby pair grid members instead of the built-in procedures discussed in this chapter.

Detaching a TimesTen database from a cache grid

Call the ttGridDetach built-in procedure to detach a grid member from the cache grid that it is attached to. If the grid member is an active standby pair, the active and standby databases must both be detached, and they must be detached separately. When a grid member has been detached, you can no longer perform operations on its global cache groups or on their cache tables. The grid member also relinquishes ownership of all cache instances that it had owned. The cache agent and replication agent processes cannot be stopped until the database detaches from its cache grid.

From the cachealone1 database, call the ttGridDetach built-in procedure as the cache manager user to detach the member from the ttGrid cache grid. For example:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttGridDetach;

To make sure that all committed updates on cache tables in the global cache groups in cachealone1 have been propagated to the cached Oracle Database tables before the TimesTen database is detached from its cache grid, specify the number of seconds to wait before executing the detach. In this example, the wait is 60 seconds:

Command> CALL ttGridDetach(,,60);

Then after the database has been detached from its grid, the replication agent running on the database can be stopped.

You can force detach a grid member that becomes unavailable but is still attached to the grid. A grid member's underlying TimesTen database is unavailable, for example, when the TimesTen system is taken offline or the database has been destroyed. Call the ttGridDetach built-in procedure as the cache manager user passing the value 1 to the force parameter from any one of the TimesTen databases that are available except from the read-only subscriber databases.

Command> CALL ttGridDetach('TTGRID_alone2_2',1);

To determine the names of all attached grid members, call the ttGridNodeStatus built-in procedure.

You can force detach a set of grid members that become unavailable but are still attached to the grid by calling the ttGridDetachList built-in procedure as the cache manager user from any one of the TimesTen databases that are available except from the read-only subscriber databases. Pass the value 1 to the force parameter.

Command> CALL ttGridDetachList('TTGRID_cacheact_3A TTGRID_cachestand_3B',1);

You can detach all of the grid members by calling the ttGridDetachAll built-in procedure. In this example, the detach operation waits 60 seconds:

Command> CALL ttGridDetachAll(60);

Stopping the replication agent

Call the ttRepStop built-in procedure to stop the replication agent. This must be done on each TimesTen database of the active standby pair including any read-only subscriber databases, and any standalone TimesTen databases that contain AWT cache groups.

From the cachealone1, cachealone2, cacheactive, cachestandby and rosubscriber databases, call the ttRepStop built-in procedure as the cache manager user to stop the replication agent on the database:

Command> CALL ttRepStop;

Dropping a cache group

Use the DROP CACHE GROUP statement to drop a cache group and its cache tables. Oracle Database objects used to manage the caching of Oracle Database data are automatically dropped when you use the DROP CACHE GROUP statement to drop a cache group, or an ALTER CACHE GROUP statement to set the autorefresh state to OFF for autorefresh cache groups.

If you issue a DROP CACHE GROUP statement on a cache group that has an autorefresh operation in progress:

- The autorefresh operation stops if the LockWait connection attribute setting is greater than 0. The DROP CACHE GROUP statement preempts the autorefresh operation.

- The autorefresh operation continues if the LockWait connection attribute setting is 0. The DROP CACHE GROUP statement is blocked until the autorefresh operation completes or the statement fails with a lock timeout error.

If cache tables are being replicated in an active standby pair and the cache tables are the only elements that are being replicated, you must drop the active standby pair using a DROP ACTIVE STANDBY PAIR statement before dropping the cache groups. If the active standby pair is a grid member, the grid member must be detached from the grid before dropping the active standby pair.

Execute the following statement as the cache manager user on the cacheactive, cachestandby and rosubscriber databases to drop the active standby pair replication scheme:

Command> DROP ACTIVE STANDBY PAIR;
Command> exit

You must unload the data in a global cache group in all grid members before dropping the cache group. Set the GlobalProcessing optimizer flag to 1 and unload the cache group:

CALL ttOptSetFlag('GlobalProcessing', 1);
UNLOAD CACHE GROUP subscriber_accounts;

Before you can drop a cache group, you must grant the DROP ANY TABLE privilege to the cache manager user. Execute the following statement as the instance administrator on the cachealone1, cachealone2, cacheactive and cachestandby databases to grant the DROP ANY TABLE privilege to the cache manager user. The following example shows the SQL statement issued from the cachealone1 database:

% ttIsql cachealone1
Command> GRANT DROP ANY TABLE TO cacheuser;
Command> exit

If you are dropping an AWT cache group, use the ttRepSubscriberWait built-in procedure to make sure that all committed updates on its cache tables have been propagated to the cached Oracle Database tables before dropping the cache group.

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> CALL ttRepSubscriberWait('_AWTREPSCHEME','TTREP','_ORACLE','sys1',-1);

The replication scheme that was created for the AWT cache group to enable committed updates on its cache tables to be asynchronously propagated to the cached Oracle tables is automatically dropped when you drop the cache group.

Use a DROP CACHE GROUP statement to drop the cache groups from the standalone TimesTen databases and the active and standby databases.

Execute the following statement as the cache manager user on the cachealone1, cachealone2, cacheactive and cachestandby databases to drop the subscriber_accounts global cache group. The following example shows the SQL statement issued from the cachealone1 database:

% ttIsql "DSN=cachealone1;UID=cacheuser;PWD=timesten;OraclePWD=oracle"
Command> DROP CACHE GROUP subscriber_accounts;

Note:
If the cache agent is stopped immediately after dropping a cache group, or altering the cache group's autorefresh state to OFF, the Oracle Database objects used to manage the caching of Oracle Database data may not have been dropped. When the cache agent is restarted, it drops the Oracle Database objects that were created for the dropped or altered cache group.

Destroying a cache grid

Call the ttGridDestroy built-in procedure to destroy a cache grid. By default, a cache grid cannot be destroyed if there are existing cache groups or attached grid members.

From any one of the TimesTen databases, except from the read-only subscriber databases, call the ttGridDestroy built-in procedure as the cache manager user to destroy the ttGrid cache grid:

Command> CALL ttGridDestroy('ttGrid');

You can force destroy a cache grid even if a grid member whose TimesTen database becomes unavailable while it contains cache groups or is attached to the grid. A TimesTen database is unavailable, for example, when the TimesTen system is taken offline or the database has been destroyed. Call the ttGridDestroy built-in procedure as the cache manager user passing the value 1 to the force parameter from any one of the TimesTen databases except from the read-only subscriber databases.

Command> CALL ttGridDestroy('ttGrid',1);

A cache grid should be destroyed only if it is no longer needed and there is no intent to attach to it again.

Stopping the cache agent

Call the ttCacheStop built-in procedure to stop the cache agent. This must be done on the active and standby databases of the active standby pair, and all standalone TimesTen databases.

From the cachealone1, cachealone2, cacheactive and cachestandby databases, issue the following built-in procedure call to stop the cache agent on the database:

Command> CALL ttCacheStop;
Command> exit

The cache agent cannot be stopped if the TimesTen database is still attached to a cache grid.

Destroying the TimesTen databases

If the TimesTen databases are no longer needed, you can use the ttDestroy utility to destroy the databases.

Note:
If the RAM policy designates that the database stays in memory, then this may prevent you from destroying the database. For example, if the RAM policy is set to always, then you must change the RAM policy to manual and run the ttAdmin -ramunload command to unload the database before destroying the database. For details on the RAM policy settings, see "Setting the RAM policy" section in the Oracle TimesTen In-Memory Database Operations Guide.

The following example shows the ttDestroy utility connecting to and then destroying the cachealone1 database:

% ttDestroy cachealone1

Dropping Oracle Database users and objects

Use SQL*Plus as the sys user to drop the timesten user, the schema user oratt, and the cache administration user cacheuser, and all objects such as tables and triggers owned by these users. Then drop the TT_CACHE_ADMIN_ROLE role, and the default tablespace cachetblsp used by the timesten user and the cache administration user including the contents of the tablespace and its data file.

% sqlplus sys as sysdba
Enter password: password
SQL> DROP USER timesten CASCADE;
SQL> DROP USER oratt CASCADE;
SQL> DROP USER cacheuser CASCADE;
SQL> DROP ROLE tt_cache_admin_role;
SQL> DROP TABLESPACE cachetblsp INCLUDING CONTENTS AND DATAFILES;
SQL> exit

Recommended method for a scheduled shutdown of an active standby pair with AWT cache groups

When you are using active standby pairs with AWT cache groups, the environment includes both an active and a standby master, potentially one or more subscribers, and at least one Oracle Database. The following is the recommended method when you initiate a scheduled shutdown of outstanding transactions in this environment. This order of events provides the time needed to finish applying outstanding transactions before shut down and minimizes the time needed to restart all components.

1. Shut down all applications.

2. Ensure that all transactions have propagated to the Oracle database.

3. Shut down TimesTen.

4. Shut down the Oracle Database.

Then, when you are ready to restart all components:

1. Restart the Oracle Database.

2. Restart TimesTen.

3. Restart any applications.

You can shut down all of these products in any order without error. The order matters only to maximize performance and reduce the need for preserving unapplied transactions. For example, when you are using AWT cache groups within the active standby pair and if you shut down the Oracle database before TimesTen, then all unapplied transactions accumulate in the TimesTen transaction logs. Thus, when you restart TimesTen and Oracle, you could potentially have a lower throughput while pending transactions are applied to the Oracle database. Thus, shutting down TimesTen before the Oracle database provides the most efficient method for your scheduled shutdown and startup. In addition, shutting down the applications before TimesTen stops any additional requests from being sent to an unavailable TimesTen database.

10 Using the Cache Advisor

The following sections describe and demonstrate how to use the TimesTen Application-Tier Database Cache Advisor (TimesTen Cache Advisor):

- Cache Advisor overview

- Setting up the Oracle Database and TimesTen host systems

- Running a SQL workload application

- Running the Cache Advisor

- Viewing the Cache Advisor reports

- Cleaning up the Oracle and TimesTen databases and host systems

Cache Advisor overview

The TimesTen Cache Advisor enables Oracle Database customers to determine whether the performance of an existing Oracle Database application can be improved if the application is used with TimesTen Cache, also referred to as a TimesTen database.

Cache Advisor generates recommendations of TimesTen cache group definitions based on the SQL usage in the Oracle Database application. It does this by evaluating either a captured SQL workload from the application or an existing SQL tuning set. Cache Advisor analyzes this information along with the schema definitions of the Oracle Database objects to determine table and column usage patterns. Cache Advisor also analyzes application performance for specified TimesTen Cache sizes, so the cache group recommendations may differ depending on the size of the specified cache. For information on SQL tuning sets, see "Managing SQL Tuning Sets" in the Oracle Database 2 Day + Performance Tuning Guide.

When evaluating the captured SQL application workload or SQL tuning set, Cache Advisor recommends either using asynchronous writethrough (AWT) cache groups or read-only cache groups in the TimesTen application. It determines the type of cache groups to use based on the number of SQL statement executions in the Oracle Database application that change data values relative to the number of SQL SELECT statement executions.

Note:
Cache Advisor evaluates DML statements (SELECT, INSERT, UPDATE and DELETE) for execution porting issues, but evaluates only SELECT statements on both TimesTen and Oracle Database for the performance comparison.
Cache Advisor evaluates each SQL statement in isolation from any other statement. If necessary, it performs a ROLLBACK after each statement completes to preserve data. If Cache Advisor were to commit all DML changes, then the data would change, which would alter the behavior of any subsequent Cache Advisor evaluations. For example, if Cache Advisor evaluates and commits a DELETE statement on Oracle Database, then when the Cache Advisor performs the evaluation again, there would be no rows to delete.

After analyzing the application workload or SQL tuning set, and comparing its performance between Oracle Database and TimesTen Cache, Cache Advisor generates an HTML report that contains performance statistics comparing Oracle Database and TimesTen Cache, definitions of the recommended cache tables in the TimesTen cache group that the application accesses, and the SQL statements that reference the cache tables. The report also shows which statements from the workload or SQL tuning set can be executed in TimesTen Cache with no changes, and which statements require modification before they can be executed. See Appendix C, "Compatibility Between TimesTen and Oracle Databases" for information about differences that may be encountered.

Cache Advisor also generates a ttIsql script that can be used to implement the recommended cache group definitions. The user-editable script contains SQL statements such as CREATE CACHE GROUP, LOAD CACHE GROUP, CREATE INDEX, CREATE SYNONYM, and CREATE VIEW.

Cache Advisor requires the use of up to three databases:

- A target Oracle database on which the user application runs and where the application schema resides. This is where the SQL workload is captured. The workload executing on this database should be as close to the production database workload as possible. In addition, the Cache Advisor relies on statistics in the Oracle target database to calculate the table sizing in TimesTen. Users should ensure statistics in the target Oracle database are collected and are up to date.

- A repository Oracle database where Cache Advisor performs analysis of the workload of SQL statements that are executed on the target Oracle database.

Note:
If the target database is part of a production system, place the Cache Advisor repository on a separate, non-production database. If the target database is part of a test system, place the Cache Advisor repository on the same database as the target to simplify setup and operation.

- A TimesTen database, also referred to as an TimesTen Cache, where Cache Advisor defines and evaluates the recommended cache groups whose cache tables correspond to the tables in the target Oracle database that the application workload accesses.

Figure 10-1 Demonstration of the three databases used by the Cache Advisor

Setting up the Oracle Database and TimesTen host systems

Before you can use Cache Advisor, you must first install TimesTen and then configure the Oracle Database and TimesTen systems.

Note:
See the Oracle TimesTen In-Memory Database Installation Guide for information about installing TimesTen.

The following sections provide an example to show how to configure each database and host in order to execute the Cache Advisor. This example uses one of the Quick Start sample programs as a demonstration for the application that executes the SQL workload.

To set up the Oracle Database and TimesTen hosts and databases, complete the following tasks:

1. Configure the target Oracle database

2. Configure the repository Oracle database

3. Configure the TimesTen database

See "Cache Advisor configuration options and usage guidelines" for details on the configuration options and usage guidelines when installing and configuring each host and database included in the Cache Advisor environment.

Configure the target Oracle database

The target Oracle database is where the application schema is defined. This is the database that the user application accesses. Cache Advisor requires that the version of the target database be Oracle Database Enterprise Edition 10g Release 2 (10.2.0.4) or later.

To set up the target database for use by TimesTen Cache, start SQL*Plus from an operating system shell on the TimesTen database system and connect to the target database as the Oracle Database sys user. In this example, the net service name of the target database is targetdb.

% cd TimesTen_install_dir/oraclescripts
% sqlplus sys@targetdb as sysdba
Enter password: password

Use SQL*Plus to create a default tablespace that is be used by both the Oracle Database timesten user and the cache administration user. This tablespace must only be used to store objects for TimesTen Cache and should not be shared with other applications. In this example, the name of the default tablespace is cachetblsp. For more information about the timesten user, see "Create users in the Oracle database".

Run the SQL*Plus script TimesTen_install_dir/oraclescripts/initCacheGlobalSchema.sql to create the timesten user and its metadata tables and the TT_CACHE_ADMIN_ROLE role that defines privileges to be granted to this user. Pass the default tablespace as an argument to the initCacheGlobalSchema.sql script.

SQL> CREATE TABLESPACE cachetblsp DATAFILE 'datfttuser.dbf' SIZE 100M;
SQL> @initCacheGlobalSchema "cachetblsp"

Next, use SQL*Plus to create a target Oracle Database user, if this user does not already exist.

Note:
Since this example is using the Quick Start sample program, the example creates oratt as the schema owner.

The target Oracle Database user owns the Oracle Database objects that are to be accessed by the SQL workload application and are candidates for caching in a TimesTen database. The target Oracle Database user is the same as the schema user that is described in "Create users in the Oracle database".

Grant this user at least the minimum set of privileges required to create tables in the Oracle database to be cached in a TimesTen database. In this example, the target Oracle Database user is oratt.

SQL> CREATE USER oratt IDENTIFIED BY oracle;
SQL> GRANT CREATE SESSION, RESOURCE TO oratt;

Then use SQL*Plus to create a cache administration user. Run the SQL*Plus script TimesTen_install_dir/oraclescripts/grantCacheAdminPrivileges.sql to grant the cache administration user the minimum set of privileges required to process cache group operations. For information on cache groups, see "Cache groups and cache tables".

Note:
The target Oracle Database user and the cache administration user must be different users. In addition, when you create the repository Cache Advisor user, this user must also be a different user.

Pass the cache administration user name as an argument to the grantCacheAdminPrivileges.sql script. In this example, the cache administration user is cacheuser and the name of its default tablespace is cachetblsp. For more information about the cache administration user, see "Create users in the Oracle database".

SQL> CREATE USER cacheuser IDENTIFIED BY oracache
DEFAULT TABLESPACE cachetblsp QUOTA UNLIMITED ON cachetblsp;
SQL> GRANT SELECT ANY TABLE, DELETE ANY TABLE,
INSERT ANY TABLE, UPDATE ANY TABLE TO cacheuser;
SQL> @grantCacheAdminPrivileges "cacheuser"

Run the SQL*Plus script TimesTen_install_dir/oraclescripts/ttca_setupTarget.sql to perform the following operations:

- Create the TTCA_TARGET_ROLE role that defines privileges to be granted to the target Oracle Database user.

- Create an Oracle directory object named TTCA_DIRECTORY that is used for file operations into and out of the target database. The ttca_setupTarget.sql script associates the TTCA_DIRECTORY directory object with the local directory that the target Cache Advisor user created earlier. See "CREATE DIRECTORY" in the Oracle Database SQL Language Reference for information about Oracle Database directory objects.

After running the ttca_setupTarget.sql script, exit the SQL*Plus session.

The following example shows the output when the TTCA_DIRECTORY object has not yet been created:

SQL> @ttca_setupTarget

This script sets up your target Oracle database for use with the TimesTen
Cache Advisor.

The target Oracle database is the application database that you wish to cache
using TimesTen Application-Tier Database Cache.

This script performs the following actions:
1. Create the TTCA_TARGET_ROLE role, if it does not already exist
2. Create a new directory object on the target Oracle database,
if directed by you to do so
3. Grant read and write access on a new or existing target Oracle database
directory object to the TTCA_TARGET_ROLE role
4. Grant the TTCA_TARGET_ROLE role to the target Oracle database user

Run this script as SYSDBA on the target database.

(You will also need to configure a repository Oracle database that you set up
with the ttca_setupRepository.sql script.)

Please enter a target Oracle database user name to access the target database:
oratt

The TimesTen Cache Advisor requires the use of a directory object on the
target Oracle database for DataPump and file operations.

An Oracle directory object is created with the CREATE DIRECTORY Oracle Data
Definition Language (DDL) statement. A directory object is identified by an
Oracle object name (up to 30 alphanumeric characters) and is associated with
a host-platform-specific directory path (up to 4000 characters).

********************************************************************************
*** Enter the directory path on the target system to use in the definition
*** of TTCA_DIRECTORY
********************************************************************************
? /mysystem/mydirectory/ttca_directory

Create TTCA_DIRECTORY directory object succeeded.

Grant READ and WRITE on TTCA_DIRECTORY directory object to TTCA_TARGET_ROLE role
succeeded.

Grant READ and WRITE on TTCA_DIRECTORY directory object to scott role succeeded.
To revoke privileges granted by this script:
REVOKE ttca_target_role FROM oratt;
DROP ROLE ttca_target_role;
REVOKE READ, WRITE ON DIRECTORY TTCA_DIRECTORY FROM oratt;
No errors.

*******************
**** All done! ****
*******************

If the TTCA_DIRECTORY object has already been created, the script notices and acknowledges that it already exists:

*** The directory object used by cache Advisor (TTCA_DIRECTORY) already exists.
*** Please press ENTER to continue
********************************************************************************
?

Configure the repository Oracle database

The repository Oracle database is where Cache Advisor performs analysis of the SQL workload that is being run on the target Oracle database. Cache Advisor also does report and script generation in the repository database, as well as store tasks. A task is an object that contains information about the workload, performance results, and Cache Advisor options that are specified by the user.

- If the target database is part of a production system, place the Cache Advisor repository on a separate, non-production database. First install and configure a repository database of Oracle Database Enterprise Edition 10g Release 2 (10.2.0.4) or later. The version of the repository database must be the same or later than the version of the target Oracle database. Because the Cache Advisor copies schema definitions from the target database to the repository database when using separate target and repository databases, the separate repository database should be devoted to the Cache Advisor. When you are ready to clean up the Cache Advisor repository, simply drop the database.

- If the target database is part of a test system, place the Cache Advisor repository on the same database as the target for simplification of setup and operation. When you are ready to clean up the Cache Advisor repository, execute the DROP USER TTCACHEADVISOR CASCADE statement.

Start SQL*Plus from an operating system shell on the TimesTen database system and connect to the repository database as the Oracle Database sys user. In this example, the net service name of the repository database is repositorydb.

% cd TimesTen_install_dir/oraclescripts
% sqlplus sys@repositorydb as sysdba
Enter password: password

You must connect to the repository database with the SYSDBA privilege.

Run the SQL*Plus script TimesTen_install_dir/oraclescripts/ttca_setupRepository.sql to perform the following operations:

- Create a user that owns the objects in the repository database used to analyze the SQL workload run on the target Oracle database, and create the ttca_ts tablespace used to store these objects.

- Create or specify an Oracle Database directory object used for file operations into and out of the repository database. The ttca_setupRepository.sql script associates the directory object with the local directory that the repository Cache Advisor user created earlier. See "CREATE DIRECTORY" in Oracle Database SQL Language Reference for information about Oracle Database directory objects.

After running the ttca_setupRepository.sql script, exit the SQL*Plus session.

SQL> @ttca_setupRepository

This script sets up your repository Oracle database for use with the TimesTen
Cache Advisor.

The repository Oracle database is used by the TimesTen Cache Advisor as
an analytical workspace.

This script performs the following actions:
1. Create repository Oracle database user TTCACHEADVISOR (or other user name
that you specify)
2. Grant read and write access on a new or existing repository Oracle database
directory object to the repository database user
3. Create tablespace TTCA_TS, if it does not exist
4. Grant required privileges to the repository database user
5. Create required tables and views owned by the repository database user

Run this script as SYSDBA on the repository database.

(You will also be using a target Oracle database that you set up
with the ttca_setupTarget.sql script.)

Press ENTER to create the repository Oracle database user with
user name TTCACHEADVISOR, or enter an alternative user name for
the repository database user:
Please enter a password for the TTCACHEADVISOR user:
Please confirm the password for the TTCACHEADVISOR user:

The TimesTen Cache Advisor requires the use of a directory object on the
repository Oracle database for DataPump and file operations.

An Oracle directory object is created with the CREATE DIRECTORY Oracle Data
Definition Language (DDL) statement. A directory object is identified by an
Oracle object name (up to 30 alphanumeric characters) and is associated with
a host-platform-specific directory path (up to 4000 characters).

********************************************************************************
*** Enter the directory path on the repository system to use in the definition
*** of TTCA_DIRECTORY
********************************************************************************
? /mysystem/mydirectory/ttca_directory

Create TTCA_TS tablespace succeeded.

Create TTCACHEADVISOR user succeeded.

Create TTCA_DIRECTORY directory object succeeded.

*******************
**** All done! ****
*******************

To employ other directories as directory objects on the repository
database, grant READ,WRITE ON DIRECTORY <directory_name> TO TTCACHEADVISOR

If the TTCA_DIRECTORY object has already been created, the script notices and acknowledges that it already exists:

*** The directory object used by cache Advisor (TTCA_DIRECTORY) already exists.
*** Please press ENTER to continue
********************************************************************************
?

If the TT_CS tablespace has already been created, the following statement does not appear in the output:

Create TTCA_TS tablespace succeeded.

Configure the TimesTen database

The TimesTen database is where Cache Advisor defines and evaluates the recommended cache groups whose cache tables correspond to the tables in the target Oracle database. The TimesTen database is a test database to be used only by Cache Advisor and should not be shared with other applications.

In the following data source name (DSN) example, the net service name of the target Oracle database is targetdb and its database character set is AL32UTF8. The TimesTen database character set must match the database character set of the target Oracle database. You can determine the database character set of an Oracle database by executing the following query in SQL*Plus as any user:

SQL> SELECT value FROM nls_database_parameters
WHERE parameter='NLS_CHARACTERSET';

In the .odbc.ini file that resides in your home directory or the TimesTen_install_dir/info/sys.odbc.ini file, create a TimesTen DSN cacheadv and set the following connection attributes:

Note:
In this example, Cache Advisor sets the CacheGridEnable attribute to 0, so that the user is not required to create a grid. For more details, see "CacheGridEnable" in the Oracle TimesTen In-Memory Database Reference.

[cacheadv]
DataStore=/users/OracleCache/cacheadv
PermSize=64
OracleNetServiceName=targetdb
DatabaseCharacterSet=AL32UTF8
CacheGridEnable=0

Note:

See "Define a DSN for the TimesTen database" for more information about defining a DSN for a TimesTen database that caches data from an Oracle database.

See "Managing TimesTen Databases" in the Oracle TimesTen In-Memory Database Operations Guide for more information about TimesTen DSNs.

Set up the TimesTen database for use by TimesTen Cache. Start the ttIsql utility on the TimesTen system from an operating system shell and connect to the cacheadv DSN as the TimesTen instance administrator user to create the TimesTen database that is to be used to cache data from the target Oracle database.

% ttIsql cacheadv

Use ttIsql to create a cache manager user, where there is a companion Oracle Database user with the same name. Grant this user at least the minimum set of privileges required to create and perform operations on cache groups. In the following example, the cache manager user name is cacheuser and the cache administration user is acting as its companion Oracle Database user.

Command> CREATE USER cacheuser IDENTIFIED BY ttcache;
Command> GRANT CREATE SESSION, CACHE_MANAGER, CREATE ANY TABLE TO cacheuser;

Note:

For more information about the cache manager user, see "Create the TimesTen users".

Next, use ttIsql to call the ttCacheUidPwdSet built-in procedure to set the cache administration user name and password. Then, exit the ttIsql session.

Command> call ttCacheUidPwdSet('cacheuser','oracache');
Command> exit

The cache administration user name and password need to be set only once in a TimesTen database. See "Set the cache administration user name and password" for information about how this setting is used in the TimesTen database.

Cache Advisor configuration options and usage guidelines

The following sections describe supported configuration options and guidelines for using the Cache Advisor:

- Supported configuration options for hosts and databases

- Restrictions and assumptions

Supported configuration options for hosts and databases

Cache Advisor supports the following configuration options for hosts and databases included in the Cache Advisor environment:

- A single Oracle database, which must be Oracle Database Enterprise Edition 10g Release 2 (10.2.0.4) or later, serves as both the target and repository databases. The target Oracle database must be a test database and not a production database.
The TimesTen database can reside either on a separate host system for a more accurate performance analysis or on the same host as the Oracle database for demonstration purposes.

This is the preferred configuration as it offers the simplest setup and operation.

- A single Oracle database, which must be Oracle Database Enterprise Edition 10g Release 2 (10.2.0.4) or later, serves as the target database with no repository or TimesTen databases.
The target database can be part of a live, production system or part of a test system. This configuration is supported only with the -export command-line option.

This configuration can capture an application SQL workload and schema definitions with deferred analysis. Use the -import option with one of the other supported configurations to perform the deferred analysis.

- The target Oracle database (which must be Oracle Database Enterprise Edition 10g Release 2 (10.2.0.4) or later), the repository Oracle database (which must be Oracle Database Enterprise Edition 10g Release 2 (10.2.0.4) or later), and the TimesTen database are all separate databases residing on the same or separate host systems.
The target Oracle database cannot be a version later than the repository Oracle database. For performance analysis with the -evalSqlPerf command-line option, the TimesTen database should reside on a separate host and the target Oracle database must be part of a test system, not a live production system. The repository database must be devoted to Cache Advisor in order to enable clean up.

This configuration offers flexibility in the allocation of resources.

Restrictions and assumptions

The design of the cache schema recommended by Cache Advisor assumes that the user application establishes a connection to the TimesTen database and a separate connection to the target Oracle database.

Cache Advisor supports most TimesTen DSN attribute settings. However, Cache Advisor does not support the following attribute settings:

- Temporary=1 (temporary or non-persistent TimesTen database)

- TypeMode=1 (TimesTen data type mode)

- DDLCommitBehavior=1 (do not automatically commit DDL statements)

- DuplicateBindMode=1 (consider dynamic parameters with the same name as identical)

- PLSQL=0 (disable the use of TimesTen PL/SQL)

- DynamicLoadEnable=0 (disable dynamic loading of data from Oracle Database tables into TimesTen cache tables)

Running a SQL workload application

This example uses the OCI version of the throughput benchmark (tptbmOCI) to generate a SQL workload on the target Oracle database.

Build and run the demo program as any operating system user on the TimesTen system. The net service name of the target database is targetdb. The target Oracle Database user is oratt. The password of the oratt user is oracle. The application table is populated with 25^2 = 625 rows and the maximum number of SQL statements per transaction is 1000.

% cd TimesTen_install_dir/quickstart/sample_code/oci
% make tptbmOCI
% tptbmOCI -service targetdb -user oratt -key 25 -max 1000
Enter password for oratt : password
...
Load the oratt.vpn_users table with 625 rows of data
Run 10000 txns with 1 process: 80% read, 20% update, 0% insert, 0% delete

Running the Cache Advisor

While the tptbmOCI workload application is running on the target Oracle database, in a separate window run the ttCacheAdvisor utility on the TimesTen system from an operating system shell as the instance administrator user. Specify the target Oracle database, repository Oracle database, and TimesTen database involved in the evaluation.

% ttCacheAdvisor -oraTarget -oraConn "oratt@targetdb" \
-oraRepository -oraConn "ttcacheadvisor@repositorydb" \
-ttConn "DSN=cacheadv;UID=cacheuser" \
-report /home/ttuser/CAreport -task sampletask -captureCursorCache 10 \
-evalSqlPerf

Enter password for Oracle user oratt@targetdb: password
31.16:21:03 Info: beginning Oracle batch operation checkAuthorization on
oratt@targetdb
31.16:21:03 Info: Oracle batch operation checkAuthorization completed
Enter password for Oracle user ttcacheadvisor@repositorydb: password
31.16:21:05 Info: beginning Oracle batch operation checkAuthorization on
ttcacheadvisor@repositorydb
31.16:21:06 Info: Oracle batch operation checkAuthorization completed
31.16:21:06 Info: beginning Oracle batch operation checkOraUser on
oratt@targetdb
31.16:21:06 Info: Oracle batch operation checkOraUser completed
31.16:21:06 Info: beginning TimesTen batch operation checkUserExists on
"dsn=cacheadv;uid=cacheuser"
31.16:21:07 Info: TimesTen batch operation checkUserExists completed

Enter password for TimesTen user cacheuser (dsn=cacheadv): password
31.16:21:10 Info: beginning TimesTen batch operation checkTTuserAuthorization
on "dsn=cacheadv;uid=cacheuser"
31.16:21:11 Info: TimesTen batch operation checkTTuserAuthorization completed
Enter password for Oracle user cacheuser@targetdb: password
31.16:21:14 Info: beginning Oracle batch operation checkTToraclepwdAttribute
on cacheuser@targetdb
31.16:21:14 Info: Oracle batch operation checkTToraclepwdAttribute completed
31.16:21:14 Info: beginning Oracle batch operation verifyTargetConfig on
oratt@targetdb
31.16:21:25 Info: Oracle batch operation verifyTargetConfig completed
...

The previous example used the ttCacheAdvisor utility options as follows:

- The -oraTarget option identifies the target Oracle database. The -oraConn option for -oraTarget specifies the target Oracle Database user and the net service name of the target database in the connection string.

- The -oraRepository option identifies the repository Oracle database. The -oraConn option for -oraRepository specifies the user that owns the objects in the repository database used to analyze the SQL workload run on the target Oracle database and the net service name of the repository database in the connection string.

- The -ttConn option identifies the TimesTen database. Specify the DSN and the cache manager user in the connection string.

- The -report option overrides the default directory location where the report files reside.

- The -task option overrides the default task name.

- The -captureCursorCache option specifies that the ttCacheAdvisor utility capture the SQL workload running on the target database for a capture window duration of 10 minutes. If a percentage of SQL statements escape capture, use a longer capture duration.

- The -evalSqlPerf option is specified to generate a performance comparison between the workload run on the target Oracle database and on the TimesTen database.

If the passwords are not specified in the connection strings for each database, the ttCacheAdvisor utility prompts for the passwords of each user connecting to the TimesTen and Oracle databases used in the Cache Advisor evaluation.

For this example, the following user passwords are requested:

- The password for the target Oracle database user. In this example, the password of oratt@targetdb is oracle.

- The password for the user that owns the objects in the repository Oracle database used to analyze the SQL workload run on the target Oracle database. In this example, the password of ttcacheadvisor@repositorydb is ttca.

- The password for the TimesTen cache manager user. In this example, the password of cacheuser is ttcache.

- The password of the cache administration user. In this example, the password of cacheuser@targetdb is oracache. This password is requested because the -evalSqlPerf option is specified to generate a performance comparison between the workload run on the target Oracle database and on the TimesTen database.

The ttCacheAdvisor utility generates periodic status messages as it analyzes the application workload running on the target database.

When ttCacheAdvisor completes, it creates an HTML report showing performance statistics as well as information such as which SQL statements from the workload can and cannot be executed in TimesTen. By default, the files that constitute the report reside in the task-name directory where the utility was invoked. In this example, the directory is specified with the -report option. To view the report, open the index.htm file in the report files directory from a web browser. The task name, by default, is userName_hostName_timestamp. In this example, the task name is overridden with the -task option.

The ttCacheAdvisor utility also generates an implementation script file named ttCacheAdvisor_taskName_timestamp.sql in the directory specified with the -report option. This script can be run with the ttIsql utility to create objects in the TimesTen database used to implement the caching of the Oracle Database objects that were accessed by the application.

% ttIsql -f ttCacheAdvisor_sampletask_20120531164101.sql
"DSN=cacheadv;UID=cacheuser;OraclePWD=oracache"

For more information about the report and implementation script, see "Viewing the Cache Advisor reports".

For information about the syntax for ttCacheAdvisor, see "ttCacheAdvisor" in the Oracle TimesTen In-Memory Database Reference.

Improve performance by using NFS or FTP for transferring data

Note:
For details on the options mentioned in this section, see "ttCacheAdvisor" in the Oracle TimesTen In-Memory Database Reference.

Cache Advisor moves data into or out of the database using DataPump. DataPump requires an Oracle directory object with an associated directory path that is local and not network mounted. By default, Cache Advisor uses the TTCA_DIRECTORY Oracle directory object, which is created with the setup scripts, with the -export and -import options to export and import information using DataPump. Also, by default, Cache Advisor uses the OCI connection specified with the -oraConn option to transfer files. While more convenient and easy to use, the mechanism that Cache Advisor uses to transfer files over the OCI connection can be approximately three times slower than NFS or ftp. File transfer performance is only affected with the -export option, -import option, or the -captureCursorCache option when the target and repository are on different databases.

Note:
Configuring data file transfer options with the -oraDirNfs or -ftp options are optional and only relevant if you want to improve file transfer performance.

To improve file transfer performance, you can optionally use the -oraDirNfs or -ftp options. The TTCA_DIRECTORY directory object is not configured for use with the -oraDirNfs or -ftp options. So, you must specify and configure an alternate directory object with the -oraDirObject option for use with the -oraDirNfs or -ftp options.

To configure the directory,

1. Log onto the Oracle database and create a new directory object. To create a directory object, execute the following command:

CREATE DIRECTORY dir_name AS /local_dir_path/subdir_path;

The directory path you specify must be a local directory and cannot be network mounted.

2. Log onto the host system where the target or repository Oracle database resides and create a directory that matches the directory path associated with the Oracle directory object. This directory can be created by any operating system user on the target system. The directory must be created on a device that is local to the host system and not network mounted.
The owner of the directory is referred to as the target Cache Advisor user. In the following example, the target Cache Advisor user is ca_usr and the directory is /local/ca_usr/ca_dir.

% mkdir /local/ca_usr/ca_dir

3. Determine the file system that the directory resides on. On Linux systems, this information can be obtained by running the df operating system command. In this example, the file system that the /local/ca_usr/ca_dir directory resides on is /dev/sda1.

4. Cache Advisor must be able to access the contents of the DataPump dump files from the host system to perform its analysis. However, the permissions placed on those files by Data Pump prevent them from being accessed through NFS or transferred to the repository system using ftp. To access the dump files from the repository system, set an access control list (ACL) on the directory where the files will reside on the target system.
As the operating system root user, enable the setting of ACLs on the file system.

# mount -o remount,acl /dev/sda1

5. Change the permissions on the directory so that only the Cache Advisor user can read from and write to it. Then, set ACLs on the directory and any files created in the directory to read, write, and execute for the Cache Advisor user and the operating system user that is running the Oracle Database server on the host system (typically the oracle user). On Linux systems, ACLs can be set by running the operating system setfacl command.

% chmod 700 /local/ca_usr/ca_dir
% setfacl -m u:ca_usr:rwx /local/ca_usr/ca_dir
% setfacl -m d:u:ca_usr:rwx /local/ca_usr/ca_dir
% setfacl -m u:oracle:rwx /local/ca_usr/ca_dir
% setfacl -m d:u:oracle:rwx /local/ca_usr/ca_dir

Viewing the Cache Advisor reports

This section provides examples of the report pages generated by the Cache Advisor. The report can be viewed using the following Web browsers:

- Firefox 3.6 or later

- Chrome 7 or later

- Safari 4 or later

To view the report, open the index.htm file in the report files directory from a Web browser.

If the -evalSqlPerf option was specified when the ttCacheAdvisor utility was executed, the report shows the average response time for the SQL SELECT statements that were executed in the target Oracle database. It also shows the average response time for these statements when executed in the TimesTen database with the user-specified cache size. The complete TimesTen Cache size is the minimum TimesTen database size required to cache all of the objects that were accessed by the SQL workload and can be supported by TimesTen.

Figure 10-2 Cache Advisor report home page

Figure 10-3 Cache Advisor findings and recommendations

You can view the SQL statements that were executed in the workload by clicking the link under the SQL Statements column on the home page that indicates the number of statements in the workload. In this case, click the link of the first 2 where it says "2 of 2".

Figure 10-4 Viewing the number of SQL statements executed in the workload

You can click an individual SQL statement to see the response time and other statistics for that statement. In this example, when you click the link of the second statement, you see the following information about the SELECT statement:

Figure 10-5 Information for a specific SQL statement executed during Cache Advisor evaluation

You can click the name of the cache group to see the definition of the cache group and its cache tables, as well as the SQL statements that referenced the cache group. In this example, the following report page appears when you click the CG1_USERSPECCACHE link:

Figure 10-6 Cache group details

Figure 10-7 SQL statements used for cache group

From the home page, you can access the text of the implementation script by clicking the "Configure an TimesTen Cache for your application" link. Then, from the next page, click the "Implementation Script" link.

Note:
For more details on the implementation script, see "Running the Cache Advisor".

The following shows an example of an implementation script:

SHOW ERRORS;
SET ECHO OFF;
SET DEFINE ON;
SET SERVEROUTPUT ON;
PROMPT Welcome to the TimesTen CacheAdvisor (ttCacheAdvisor).
PROMPT
PROMPT ttCacheAdvisor generated this script to implement its recommendations.
PROMPT The first step is to create the necessary TimesTen user accounts to
PROMPT receive the recommended cache groups and associated indexes, views,
PROMPT materialized views and sequences. This script will now prompt you for
PROMPT the password for each account to be created. Be sure to use the same
PROMPT password for each TimesTen user account as on Oracle.
PROMPT
PROMPT NOTE: If an error occurs or for any reason, you can abort this script at
PROMPT any time by pressing the control and C keys (^C) simultaneously.
PROMPT Sometimes it is necessary to press ^C multiple times followed by
PROMPT pressing ENTER.
ACCEPT ORAUSER_pwd CHAR PROMPT 'Enter user ORAUSER password (use same password
as on Oracle)? 'HIDE
ACCEPT ORAUSER_pwd2 CHAR PROMPT 'Confirm user ORAUSER password? ' HIDE
COMMIT;
EXEC createUser ('ORAUSER','&&ORAUSER_pwd','&&ORAUSER_pwd2');
COMMIT;
DROP PROCEDURE createUser;
ACCEPT answer CHAR PROMPT 'Press ENTER to continue, ^C to abort:'
EXEC execImmediate ('CALL ttCacheStart');
EXEC execImmediate ('CALL ttRepStop');
EXEC execImmediate ('DROP CACHE GROUP CG1_USERSPECCACHE');
COMMIT;
COMMIT;
CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP CG1_USERSPECCACHE
FROM ORAUSER.VPN_USERS
( VPN_ID NUMBER(5,0) NOT NULL,
VPN_NB NUMBER(5,0) NOT NULL,
DIRECTORY_NB CHAR(10 BYTE) NOT NULL,
LAST_CALLING_PARTY CHAR(10 BYTE) NOT NULL,
DESCR CHAR(100 BYTE) NOT NULL,
PRIMARY KEY (VPN_ID, VPN_NB)
);
COMMIT;
LOAD CACHE GROUP CG1_USERSPECCACHE COMMIT EVERY 256 ROWS;
COMMIT;
CALL ttOptUpdateStats ('ORAUSER.VPN_USERS',1);
COMMIT;
COMMIT;
COMMIT;
EXEC execImmediate ('CALL ttRepStart');
COMMIT;

The name of the script is ttCacheAdvisor_task-name_timestamp.sql and it resides in the directory where the ttCacheAdvisor utility was invoked. This script can be run with the ttIsql utility to create objects in the TimesTen database used to implement the caching of the Oracle Database objects that were accessed by the application.

% ttIsql -f ttCacheAdvisor_sampletask_20120531164101.sql
"DSN=cacheadv;UID=cacheuser;OraclePWD=oracache"

You can obtain database and system information about the target Oracle database (Workload Collection), repository Oracle database and TimesTen database (Client) by clicking the "Click here for information about the configuration that was used to generate this report" link from the home page.

Figure 10-8 Configuration overview page

Figure 10-9 Repository and client configuration information

Cleaning up the Oracle and TimesTen databases and host systems

Complete the following tasks to restore the Oracle Database and TimesTen systems to their original state after you have finished evaluating the application workload that was run on the target Oracle database:

1. Clean up the target Oracle database and host system

2. Clean up the repository Oracle database and host system

3. Clean up the TimesTen database and host system

Clean up the target Oracle database and host system

Start SQL*Plus from an operating system shell on the TimesTen database system and connect to the target Oracle database as the sys user. Then, use SQL*Plus as follows to clean up the target Oracle database and its host system:

1. Drop the timesten user, the oratt target Oracle Database user (if you created this user because it did not exist before configuring the target database), and the cacheuser cache administration user.

% sqlplus sys@targetdb as sysdba
Enter password: password
SQL> DROP USER timesten CASCADE;
SQL> DROP USER oratt CASCADE;
SQL> DROP USER cacheuser CASCADE;

Note:
Specifying CASCADE in a DROP USER statement drops all objects, such as tables owned by the user, before dropping the user itself.

2. Drop the TT_CACHE_ADMIN_ROLE role, the TTCA_TARGET_ROLE role, and the TTCA_DIRECTORY directory object.

SQL> DROP ROLE TT_CACHE_ADMIN_ROLE;
SQL> DROP ROLE TTCA_TARGET_ROLE;
SQL> DROP DIRECTORY TTCA_DIRECTORY;
SQL> exit

3. Drop the cachetblsp default tablespace used by the timesten user and cache administration user, including the contents of the tablespace and its data file. Exit the SQL*Plus session.

SQL> DROP TABLESPACE cachetblsp INCLUDING CONTENTS AND DATAFILES;
SQL> exit

Note:
The above steps do not drop the schemas that were created for the workload by the Cache Advisor. You can keep the schemas for use by another application workload, if they use the same schemas, or if you want to re-execute the same workload after re-creating the user and tablespace. If not, you can either manually drop the schemas created or, if the target database is a test database, destroy the database.

Clean up the repository Oracle database and host system

If the repository resides on a separate, devoted Oracle database, drop the repository database.

If the repository resides in the same Oracle database as the target, start SQL*Plus from an operating system shell on the TimesTen database system and connect to the repository Oracle database as the sys user. Use SQL*Plus as follows to clean up the repository Oracle database and its host system:

1. Drop the ttcacheadvisor user that owns the objects in the repository database used to analyze the SQL workload run on the target Oracle database.

% sqlplus sys@repositorydb as sysdba
Enter password: password
SQL> DROP USER ttcacheadvisor CASCADE;

2. Drop the TTCA_DIRECTORY directory object.

SQL> DROP DIRECTORY TTCA_DIRECTORY;

3. Drop the ttca_ts tablespace used by the ttCacheAdvisor user, including the contents of the tablespace and its data file. Exit the SQL*Plus session.

SQL> DROP TABLESPACE ttca_ts INCLUDING CONTENTS AND DATAFILES;
SQL> exit

Clean up the TimesTen database and host system

Start the ttIsql utility and connect to the cacheadv DSN as the TimesTen instance administrator user. Perform the following to clean up the TimesTen database:

1. Use ttIsql to grant the DROP ANY TABLE privilege to the cache manager user so that this user can drop the underlying cache tables when dropping the cache groups. Then, exit this ttIsql session.

% ttIsql cacheadv
Command> GRANT DROP ANY TABLE TO cacheuser;
Command> exit

2. Start the ttIsql utility and connect to the cacheadv DSN as the cache manager user. The password of the TimesTen cache manager user cacheuser is ttcache. Use ttIsql to call the ttRepStop built-in procedure to stop the replication agent on the TimesTen database. Drop the cg1_userspeccache AWT cache group. Call the ttCacheStop built-in procedure to stop the cache agent on the TimesTen database. Exit this ttIsql session.

% ttIsql "DSN=cacheadv;UID=cacheuser;OraclePWD=oracache"
Enter password for 'cacheuser': password
Command> call ttRepStop;
Command> DROP CACHE GROUP cg1_userspeccache;
Command> call ttCacheStop;
Command> exit

3. Use the ttDestroy utility to connect to the cacheadv DSN and destroy the TimesTen database.

% ttDestroy cacheadv

11 Using TimesTen Application-Tier Database Cache in an Oracle RAC Environment

The following sections describe how to use TimesTen Application-Tier Database Cache (TimesTen Cache) in an Oracle Real Application Clusters (Oracle RAC) environment:

- How TimesTen Cache works in an Oracle RAC environment

- Restrictions on using TimesTen Cache in an Oracle RAC environment

- Setting up TimesTen Cache in an Oracle RAC environment

How TimesTen Cache works in an Oracle RAC environment

Oracle RAC enables multiple Oracle Database instances to access one Oracle database with shared resources, including all data files, control files, PFILEs and redo log files that reside on cluster-aware shared disks. Oracle RAC handles read/write consistency and load balancing while providing high availability.

Fast Application Notification (FAN) is an Oracle RAC feature that was integrated with Oracle Call Interface (OCI) in Oracle Database 10g Release 2. FAN publishes information about changes in the cluster to applications that subscribe to FAN events. FAN prevents unnecessary operations such as the following:

- Attempts to connect when services are down

- Attempts to finish processing a transaction when the server is down

- Waiting for TCP/IP timeouts

See Oracle Real Application Clusters Administration and Deployment Guide for more information about Oracle RAC and FAN.

TimesTen Cache uses OCI integrated with FAN to receive notification of Oracle Database events. With FAN, TimesTen Cache detects connection failures within a minute. Without FAN, it can take several minutes for TimesTen Cache to receive notification of an Oracle Database failure. Without FAN, TimesTen Cache detects a connection failure the next time the connection is used or when a TCP/IP timeout occurs. TimesTen Cache can recover quickly from Oracle Database failures without user intervention.

TimesTen Cache also uses Transparent Application Failover (TAF), which is a feature of Oracle Net Services that enables you to specify how you want applications to reconnect after a failure. See Oracle Database Net Services Administrator's Guide for more information about TAF. TAF attempts to reconnect to the Oracle database for four minutes. If this is not successful, the cache agent restarts and attempts to reconnect with the Oracle database every minute.

Note:
You can configure how long TAF retries when establishing a connection with the AgentFailoverTimeout parameter. For details, see "Setting up TimesTen Cache in an Oracle RAC environment".

OCI applications can use one of the following types of Oracle Net failover functionality:

- None: No failover functionality is used. This can also be explicitly specified to prevent failover from happening. This is the default failover functionality.

- Session: If an application's connection is lost, a new connection is automatically created for the application. This type of failover does not attempt to recover selects.

- Select: This type of failover enables applications that began fetching rows from a cursor before failover to continue fetching rows after failover.

The behavior of TimesTen Cache depends on the actions of TAF and how TAF is configured. By default, TAF and FAN callbacks are installed if you are using TimesTen Cache in an Oracle RAC environment. If you do not want TAF and FAN capabilities, set the RACCallback connection attribute to 0.

Table 11-1 shows the behaviors of TimesTen Cache operations in an Oracle RAC environment with different TAF failover types.

Table 11-1 Behavior of TimesTen Cache operations in an Oracle RAC environment

Operation

TAF Failover Type

Behavior After a Failed Connection on the Oracle Database

Autorefresh

None

The cache agent automatically stops, restarts and waits until a connection can be established on the Oracle database. This behavior is the same as in a non-Oracle RAC environment.

No user intervention is needed.

Autorefresh

Session

One of the following occurs:

- All failed connections are recovered. Autorefresh operations that were in progress are rolled back and retried.

- If TAF times out or cannot recover the connection, the cache agent automatically stops, restarts and waits until a connection can be established on the Oracle database.

- In all cases, no user intervention is needed.

Autorefresh

Select

One of the following occurs:

- Autorefresh operations resume from the point of connection failure.

- Autorefresh operations that were in progress are rolled back and retried.

- If TAF times out or cannot recover the connection, the cache agent automatically stops, restarts and waits until a connection can be established on the Oracle database.

- In all cases, no user intervention is needed.

AWT

None

The receiver thread of the replication agent for the AWT cache group exits. A new thread is spawned and tries to connect to the Oracle database.

No user intervention is needed.

AWT

Session, Select

One of the following occurs:

- If the connection is recovered and there are uncommitted DML operations in the transaction, the transaction is rolled back and then reissued.

- If the connection is recovered and there are no uncommitted DML operations, new operations can be issued without rolling back.

In all cases, no user intervention is needed.

SWT, propagate, flush, and passthrough

None

The application is notified of the connection loss. The cache agent disconnects from the Oracle database and the current transaction is rolled back. All modified session attributes are lost.

During the next passthrough operation, the cache agent tries to reconnect to the Oracle database. This behavior is the same as in a non-Oracle RAC environment.

No user intervention is needed.

SWT, propagate, flush and passthrough

SWT, propagate and flush

Session

Select

One of the following occurs:

- The connection to the Oracle database is recovered. If there were open cursors, DML or lock operations on the lost connection, an error is returned and the user must roll back the transaction before continuing. Otherwise, the user can continue without rolling back.

- If TAF times out or cannot recover the connection, the application is notified of the connection loss. The cache agent disconnects from the Oracle database and the current transaction is rolled back. All modified session attributes are lost.
During the next passthrough operation, the cache agent tries to reconnect to the Oracle database.

In this case, no user intervention is needed.

Passthrough

Select

The connection to the Oracle database is recovered. If there were DML or lock operations on the lost connection, an error is returned and the user must roll back the transaction before continuing. Otherwise, the user can continue without rolling back.

Load and refresh

None

The application receives a loss of connection error.

Load and refresh

Session

One of the following occurs:

- The load or refresh operation succeeds.

- An error is returned stating that a fetch operation on Oracle Database cannot be executed.

Load and refresh

Select

One of the following occurs:

- If the Oracle Database cursor is open and the cursor is recovered, or if the Oracle Database cursor is not open, then the load or refresh operation succeeds.

- An error is returned if TAF was unable to recover either the session or open Oracle Database cursors.

Note: An error is less likely to be returned than if the TAF failover type is Session.

Restrictions on using TimesTen Cache in an Oracle RAC environment

TimesTen Cache support of Oracle RAC has the following restrictions:

- TimesTen Cache behavior is limited to Oracle RAC, FAN and TAF capabilities. For example, if all nodes for a service fail, the service is not restarted. TimesTen Cache waits for the user to restart the service.

- TAF does not recover ALTER SESSION operations. The user is responsible for restoring changed session attributes after a failover.

- TimesTen Cache uses OCI integrated with FAN. This interface automatically spawns a thread to wait for an Oracle Database event. This is the only TimesTen Cache feature that spawns a thread in a TimesTen direct link application. Adapt your application to account for this thread creation. If you do not want the extra thread, set the RACCallback connection attribute to 0 so that TAF and FAN are not used.

Setting up TimesTen Cache in an Oracle RAC environment

After you install Oracle RAC and TimesTen Cache, perform the following to set up an TimesTen Cache for an Oracle RAC environment:

1. On TimesTen, set the TAF timeout, in minutes, with the ttCacheConfig AgentFailoverTimeout parameter. The AgentFailoverTimeout parameter configures how long TAF retries when establishing a connection. TAF attempts to reconnect to the Oracle database for the duration of this timeout. The default is four minutes. If this is not successful, the cache agent restarts and attempts to reconnect with the Oracle database every minute; the replication agent restarts any threads that cannot connect to the Oracle database. For more details, see "ttCacheConfig" in the Oracle TimesTen In-Memory Database Reference.

2. Make sure that the TimesTen daemon, the cache agent, and the following Oracle Database components are started:

- Oracle Database instances

- Oracle Database listeners

- Oracle Database service that is used for TimesTen Application-Tier Database Cache

3. Verify that the TimesTen RACCallback connection attribute is set to 1 (default). For more details, see "RACCallback" in the Oracle TimesTen In-Memory Database Reference.

4. Use the DBMS_SERVICE.MODIFY_SERVICE function or Oracle Enterprise Manager to enable publishing of FAN events. This changes the value in the AQ_HA_NOTIFICATIONS column of the Oracle Database ALL_SERVICES view to YES.
See Oracle Database PL/SQL Packages and Types Reference for more information about the DBMS_SERVICE Oracle Database PL/SQL package.

5. Enable TAF on the Oracle Database service used for TimesTen Cache with one of the following methods:

- Create a service for TimesTen in the Oracle Database tnsnames.ora file with the following settings:

- LOAD_BALANCE=ON (optional)

- FAILOVER_MODE=(TYPE=SELECT) or FAILOVER_MODE=(TYPE=SESSION)

- Use the DBMS_SERVICE.MODIFY_SERVICE function to set the TAF failover type.
See Oracle Database Net Services Administrator's Guide for more information about enabling TAF.

6. If you have a TimesTen direct link application, link it with a thread library so that it receives FAN notifications. FAN spawns a thread to monitor for failures.

12 Using TimesTen Application-Tier Database Cache with Data Guard

This chapter describes how to configure TimesTen Application-Tier Database Cache (TimesTen Cache) to work with either synchronous Data Guard or Data Guard used during planned maintenance. It includes the following topics:

- Components of MAA for TimesTen Application-Tier Database Cache

- How TimesTen Cache works with Data Guard

Components of MAA for TimesTen Application-Tier Database Cache

Oracle Maximum Availability Architecture (MAA) is Oracle Database's best practices blueprint based on proven Oracle Database high availability (HA) technologies and recommendations. The goal of MAA is to achieve the optimal high availability architecture at the lowest cost and complexity.

To be compliant with MAA, TimesTen Cache must support Oracle Real Application Clusters (Oracle RAC) and Oracle Data Guard, as well as have its own HA capability. TimesTen Cache provides its own HA capability through active standby pair replication of cache tables in read-only and AWT cache groups. See "Using TimesTen Application-Tier Database Cache in an Oracle RAC Environment" for more information on TimesTen Cache and Oracle RAC.

Oracle Data Guard provides the management, monitoring, and automation software infrastructure to create and maintain one or more synchronized standby databases to protect data from failures, disasters, errors and corruptions. If the primary database becomes unavailable because of a planned or an unplanned outage, Data Guard can switch any standby database to the primary role, thus minimizing downtime and preventing any data loss. For more information about Data Guard, see Oracle Data Guard Concepts and Administration.

The MAA framework for TimesTen Cache supports cache tables in explicitly loaded read-only and AWT cache groups. For cache tables in dynamic cache groups of any cache group type, SWT cache groups, and user managed cache groups that use the AUTOREFRESH cache group attribute, TimesTen Cache cannot access the Oracle database during a failover and switchover because cache applications wait until the failover and switchover completes.

In general, however, all cache groups types are supported with synchronous Data Guard or Data Guard during planned maintenance.

How TimesTen Cache works with Data Guard

TimesTen Cache works with synchronous physical standby failover and switchover and logical standby switchover as long as the object IDs for cached Oracle Database tables remain the same on the primary and standby databases. Object IDs can change if the table is dropped and re-created, altered, or a truncated flashback operation or online segment shrink is executed.

During a transient upgrade, a physical standby database is transformed into a logical standby database. For the time that the standby database is logical, the user must ensure that the object IDs of the cached Oracle Database tables do not change. Specifically, tables that are cached should not be dropped and re-created, truncated, altered, flashed back or have an online segment shrunk.

Configuring the Oracle databases

In order for TimesTen Cache to fail over and switch over properly, configure the Oracle primary and standby databases using the following steps:

1. The Data Guard configuration must be managed by the Data Guard Broker so that the TimesTen Cache daemon processes and application clients respond faster to failover and switchover events.

2. If you are configuring an Oracle RAC database, use the Oracle Enterprise Manager Cluster Managed Database Services Page to create database services that TimesTen Cache and its client applications use to connect to the Oracle primary database. See "Introduction to Automatic Workload Management" in Oracle Real Application Clusters Administration and Deployment Guide for information about creating database services.

3. If you created the database service in step 2, use the MODIFY_SERVICE function of the DBMS_SERVICE PL/SQL package to modify the service to enable high availability notification to be sent through Advanced Queuing (AQ) by setting the aq_ha_notifications attribute to TRUE. To configure server side TAF settings, set the failover attributes, as shown in the following example:

BEGIN
DBMS_SERVICE.MODIFY_SERVICE
(service_name => 'DBSERV',
goal => DBMS_SERVICE.GOAL_NONE,
dtp => false,
aq_ha_notifications => true,
failover_method => 'BASIC',
failover_type => 'SELECT',
failover_retries => 180,
failover_delay => 1);
END;

4. If you did not create the database service in step 2, use the CREATE_SERVICE function of the DBMS_SERVICE PL/SQL package to create the database service, enable high availability notification, and configure server side TAF settings:

BEGIN
DBMS_SERVICE.CREATE_SERVICE
(service_name => 'DBSERV',
network_name => 'DBSERV',
goal => DBMS_SERVICE.GOAL_NONE,
dtp => false,
aq_ha_notifications => true,
failover_method => 'BASIC',
failover_type => 'SELECT',
failover_retries => 180,
failover_delay => 1);
END;

5. Create two triggers to relocate the database service to a Data Guard standby database (Oracle RAC or non-Oracle RAC) after it has switched to the primary role. The first trigger fires on the system start event and starts up the DBSERV service:

CREATE OR REPLACE TRIGGER manage_service
AFTER STARTUP ON DATABASE
DECLARE
role VARCHAR(30);
BEGIN
SELECT database_role INTO role FROM v$database;
IF role = 'PRIMARY' THEN
dbms_service.start_service('DBSERV');
END IF;
END;

The second trigger fires when the standby database remains open during a failover and switchover upon a database role change. It relocates the DBSERV service from the old primary to the new primary database and disconnects any connections to that service on the old primary database so that TimesTen Cache and its client applications can reconnect to the new primary database:

CREATE OR REPLACE TRIGGER relocate_service
AFTER DB_ROLE_CHANGE ON DATABASE
DECLARE
role VARCHAR(30);
BEGIN
SELECT database_role INTO role FROM v$database;
IF role = 'PRIMARY' THEN
dbms_service.start_service('DBSERV');
ELSE
dbms_service.stop_service('DBSERV');
dbms_lock.sleep(2);
FOR x IN (SELECT s.sid, s.serial#
FROM v$session s, v$process p
WHERE s.service_name='DBSERV' AND s.paddr=p.addr)
LOOP
BEGIN
EXECUTE IMMEDIATE
'ALTER SYSTEM DISCONNECT SESSION
''' || x.sid || ','|| x.serial# || ''' IMMEDIATE';
EXCEPTION WHEN OTHERS THEN
BEGIN
DBMS_OUTPUT.PUT_LINE(DBMS_UTILITY.FORMAT_ERROR_STACK);
END;
END;
END LOOP;
END IF;
END;

6. As an option, to reduce the performance impact to TimesTen Cache applications and minimize the downtime during a physical or logical standby database switchover, run the following procedure right before initiating the Data Guard switchover to a physical or logical standby database:

DECLARE
role varchar(30);
BEGIN
SELECT database_role INTO role FROM v$database;
IF role = 'PRIMARY' THEN
dbms_service.stop_service('DBSERV');
dbms_lock.sleep(2);
FOR x IN (SELECT s.sid, s.serial#
FROM v$session s, v$process p
WHERE s.service_name='DBSERV' AND s.paddr=p.addr)
LOOP
BEGIN
EXECUTE IMMEDIATE
'ALTER SYSTEM DISCONNECT SESSION
''' || x.sid || ',' || x.serial# || ''' IMMEDIATE';
EXCEPTION WHEN OTHERS THEN
BEGIN
DBMS_OUTPUT.PUT_LINE(DBMS_UTILITY.FORMAT_ERROR_STACK);
END;
END;
END LOOP;
ELSE
dbms_service.start_service('DBSERV');
END IF;
END;

This procedure should be executed first on the physical or logical standby database, and then on the primary database, right before the switchover process. Before executing the procedure for a physical standby database switchover, Active Data Guard must be enabled on the physical standby database.

Before performing a switchover to a logical standby database, stop the Oracle Database service for TimesTen on the primary database and disconnect all sessions connected to that service. Then start the service on the standby database.

At this point, the cache applications try to reconnect to the standby database. If a switchover occurs, there is no wait required to migrate the connections from the primary database to the standby database. This eliminates the performance impact on TimesTen Cache and its applications.

See the Maximum Availability Architecture, Oracle Best Practices for High Availability white paper for more information.

Configuring the TimesTen database

Configure TimesTen to receive notification of FAN HA events and to avoid reconnecting to a failed Oracle Database instance. Use the Oracle Client shipped with TimesTen Cache.

1. Create an Oracle Net service name that includes all primary and standby hosts in ADDRESS_LIST. For example:

DBSERV =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = PRIMARYDB)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = STANDBYDB)(PORT = 1521))
(LOAD_BALANCE = yes)
)
(CONNECT_DATA= (SERVICE_NAME=DBSERV))
)

2. In the client's sqlnet.ora file, set the SQLNET.OUTBOUND_CONNECT_TIMEOUT parameter to enable clients to quickly traverse an address list in the event of a failure. For example, if a client attempts to connect to a host that is unavailable, the connection attempt is bounded to the time specified by the SQLNET.OUTBOUND_CONNECT_TIMEOUT parameter, after which the client attempts to connect to the next host in the address list. Connection attempts continue for each host in the address list until a connection is made.
Setting the SQLNET.OUTBOUND_CONNECT_TIMEOUT parameter to a value of 3 seconds suffices in most environments. For example, add the following entry to the sqlnet.ora file:

SQLNET.OUTBOUND_CONNECT_TIMEOUT=3

A Procedure and Privileges for Caching Oracle Database Data in TimesTen

The following sections provide a quick reference on the steps for creating a cache environment as well as the privileges required to do so:

- Quick reference to cache Oracle Database data in TimesTen

- Required privileges for the cache administration user and the cache manager user

Quick reference to cache Oracle Database data in TimesTen

The following section provides a quick reference on the steps necessary when setting up an environment that caches Oracle Database data in a TimesTen in-memory database. For a detailed explanation and examples for each step, see Chapter 2, "Getting Started", Chapter 3, "Setting Up a Caching Infrastructure", and Chapter 4, "Defining Cache Groups".

Perform the following on the Oracle database:

1. Create a default tablespace to be used for storing TimesTen Application-Tier Database Cache management objects.

2. Create the timesten user, Oracle Database tables owned by the timesten user, and the TT_CACHE_ADMIN_ROLE role that defines privileges on these Oracle Database tables by running the SQL*Plus script TimesTen_install_dir/oraclescripts/initCacheGlobalSchema.sql as the sys user.

3. As the sys user, create one or more schema users to own the cached Oracle Database tables (may be existing users).

4. As the sys user, create the cache administration user that creates, owns, and maintains Oracle Database objects that store information used to manage a specific cache grid (if one is defined) and enforce predefined behaviors of particular cache group types. In the CREATE USER statement for the cache administration user, designate the tablespace that was created for the timesten user as the default tablespace for the cache administration user.
See "Create the Oracle database users" for more information about the Oracle Database users.

5. As the sys user, run the TimesTen_install_dir/oraclescripts/grantCacheAdminPrivileges.sql script to grant the cache administration user the privileges required to perform any cache grid operations (if one is defined), create the desired types of cache groups, and perform operations on the cache groups. Alternatively, you can manually create each Oracle Database object.
See "Automatically create Oracle Database objects used to manage data caching" or "Manually create Oracle Database objects used to manage data caching" to determine the appropriate script to run.

If you are manually creating the Oracle Database objects, you also need to run the TimesTen_install_dir/oraclescripts/initCacheGridSchema.sql script to create the Oracle Database tables used to store information about TimesTen databases that are associated with a particular cache grid.

6. Some privileges cannot be granted until the cached Oracle Database tables have been created. To grant these privileges, execute GRANT statements as the sys user.
See "Required privileges for the cache administration user and the cache manager user" for more information about the privileges that must be granted to the cache administration user to perform particular cache operations.

Perform the following on the TimesTen database:

1. Define a DSN that references the TimesTen database that is to be used to cache data from an Oracle database.

1. Set the OracleNetServiceName connection attribute to the Oracle Net service name that references the Oracle database instance.

2. Set the DatabaseCharacterSet connection attribute to the Oracle database character set. The TimesTen database character set must match the Oracle database character set.

3. Then, connect to the DSN to create the database if this is a standalone database or is to be an active database of an active standby pair.

See "Define a DSN for the TimesTen database" for more information about defining a DSN for a TimesTen database that is to be used to cache data from an Oracle database.

2. Create the following users in the TimesTen database:

- Cache manager user
This user must have the same name as a companion Oracle Database user that can access the cached Oracle Database tables. The companion Oracle Database user can be the cache administration user, a schema user, or some other existing user. The password of the cache manager user and the Oracle Database user with the same name can be different.

- One or more cache table users who own the TimesTen cache tables
These users must have the same name as the Oracle Database schema users who own the cached Oracle Database tables. The password of a cache table user and the Oracle Database user with the same name can be different.

Execute CREATE USER statements as the instance administrator.

See "Create the TimesTen users" for more information about the TimesTen users.

3. Grant the cache manager user the privileges required to perform the cache grid operations, create the desired types of cache groups, and perform operations on the cache groups. Execute GRANT statements as the instance administrator.
See "Required privileges for the cache administration user and the cache manager user" for more information about the privileges that must be granted to the cache manager user to perform particular cache operations.

4. Set the cache administration user name and password in the TimesTen database either by calling the ttCacheUidPwdSet built-in procedure as the cache manager user or running a ttAdmin -cacheUidPwdSet utility command as a TimesTen external user with the CACHE_MANAGER privilege.
See "Set the cache administration user name and password" for more information about setting the cache administration user name and password in a TimesTen database.

5. If you are going to use a cache grid for global cache groups, then perform the following:

1. Create a cache grid by calling the ttGridCreate built-in procedure in the TimesTen database as the cache manager user.
See "Create a cache grid" for more information about creating a cache grid.

2. Associate the TimesTen database with the cache grid by calling the ttGridNameSet built-in procedure in the TimesTen database as the cache manager user.
See "Associate a TimesTen database with a cache grid" for more information about associating a TimesTen database with a cache grid.

6. Start the cache agent on the TimesTen database either by calling the ttCacheStart built-in procedure as the cache manager user or running a ttAdmin -cacheStart utility command as a TimesTen external user with the CACHE_MANAGER privilege.
See "Managing the cache agent" for more information about starting a cache agent on a TimesTen database.

7. Design the schema for the cache groups by determining which Oracle Database tables to cache and within those tables, which columns and rows to cache. For multiple table cache groups, determine the relationship between the tables by defining which table is the root table, which tables are direct child tables of the root table, and which tables are the child tables of other child tables. For each cached column, determine the TimesTen data type to which the Oracle Database data type should be mapped.
See "Mappings between Oracle Database and TimesTen data types" for a list of valid data type mappings between the Oracle and TimesTen databases.

For each cache group, determine what type to create (read-only, SWT, AWT, user managed) based on the application requirements and objectives. Also, determine whether each cache group is to be explicitly loaded or dynamic, and local or global.

Then, create the cache groups.

See "Creating a cache group" for more information about creating a cache group.

8. If this TimesTen database is intended to be an active database of an active standby pair, create an active standby pair replication scheme in the database.

9. If the TimesTen database contains an active standby pair replication scheme or at least one AWT cache group, start the replication agent on the database either by calling the ttRepStart built-in procedure as the cache manager user or running a ttAdmin -repStart utility command as a TimesTen external user with the CACHE_MANAGER privilege.
See "Managing the replication agent" for more information about starting a replication agent on a TimesTen database.

10. If the TimesTen database contains at least one global cache group, attach the TimesTen database to the cache grid that the database associated with by calling the ttGridAttach built-in procedure as the cache manager user.
See "Attach a TimesTen database to a cache grid" for more information about attaching a TimesTen database to a cache grid.

11. Manually load the cache tables in explicitly loaded cache groups using LOAD CACHE GROUP statements, and load the cache tables in dynamic cache groups using proper SELECT, UPDATE or INSERT statements.
See "Loading and refreshing a cache group" for more information about manually loading cache tables in a cache group.

See "Dynamically loading a cache instance" for more information about dynamically loading cache tables in a dynamic cache group.

12. If using a cache grid, you can add subsequent standalone TimesTen databases can as members to an existing cache grid.
See "Creating and configuring a subsequent standalone TimesTen database" for details about creating another standalone TimesTen database and adding that database to an existing cache grid.

13. An active standby pair can be added as a member to an existing cache grid to achieve high availability by replicating the cache tables to another TimesTen database.
See "Create and configure the active database" for details about creating an active database and adding the database to an existing cache grid.

To create the standby database from the active database, create a DSN for the standby database, and then run a ttRepAdmin -duplicate utility command on the standby database system as a TimesTen external user with the ADMIN privilege. For the command to succeed, the cache manager user in the active database must be granted the ADMIN privilege. Then, configure the database and add it as a member to the grid.

See "Create and configure the standby database" for details about creating a standby database and adding the database to an existing cache grid.

To create an optional read-only subscriber database from the standby database, create a DSN for the subscriber database. Then, run a ttRepAdmin -duplicate utility command on the subscriber database system as a TimesTen external user with the ADMIN privilege. For the command to succeed, the cache manager user in the standby database must be granted the ADMIN privilege. Then, start the replication agent on the database.

See "Create and configure the read-only subscriber database" for details about creating a read-only subscriber database for an active standby pair.

Required privileges for the cache administration user and the cache manager user

The privileges that the Oracle Database users require depends on the types of cache groups you create and the operations that you perform on the cache groups. The privileges required for the cache administration user are listed in the first column and the privileges required for the TimesTen cache manager user for each cache operation are listed in the second column in Table A-1.

Table A-1 Oracle Database and TimesTen user privileges required for cache operations

Cache operation

Privileges required for Oracle Database cache administration userFoot 1

Privileges required for TimesTen cache manager userFoot 2

Initialize the cache administration user. The grantCacheAdminPrivileges.sql script grants these privileges to the cache administration user.

CREATE SESSION

TT_CACHE_ADMIN_ROLE

EXECUTE ON SYS.DBMS_LOCK

RESOURCEFootref 4

CREATE PROCEDURE

CREATE ANY TRIGGERFoot 3 ,Footref 4

EXECUTE ON SYS.DBMS_LOB

SELECT ON SYS.ALL_OBJECTS

SELECT ON SYS.ALL_SYNONYMS

CREATE TYPE

SELECT ON SYS.GV_$LOCK

SELECT ON SYS.GV_$SESSION

SELECT ON SYS.DBA_DATA_FILES

SELECT ON SYS.USER_USERS

SELECT ON SYS.USER_FREE_SPACE

SELECT ON SYS.USER_TS_QUOTAS

SELECT ON SYS.USER_SYS_PRIVS

Permissions for the default tablespace

Set the cache administration user name and password with either:

- Call the ttCacheUidPwdSet built-in procedure.

- Run the ttAdmin -cacheUidPwdSet utility command.

- CREATE SESSION

- RESOURCEFoot 4

CACHE_MANAGER

Get the cache administration user name with either:

- Call the ttCacheUidGet built-in procedure

- Run the ttAdmin -cacheUidGet utility command

None

CACHE_MANAGER

Create a cache grid:

- Call the ttGridCreate built-in procedure.

- CREATE SESSION

- TT_CACHE_ADMIN_ROLE role

- RESOURCEFootref 4

CACHE_MANAGER

Associate a TimesTen database with a cache grid:

- Call the ttGridNameSet built-in procedure.

- CREATE SESSION

- TT_CACHE_ADMIN_ROLE role

CACHE_MANAGER

Attach a TimesTen database to a cache grid:

- Call the ttGridAttach built-in procedure.

- CREATE SESSION

- TT_CACHE_ADMIN_ROLE role

CACHE_MANAGER

Detach a TimesTen database from a cache grid:

- Call the ttGridDetach built-in procedure.

- CREATE SESSION

- TT_CACHE_ADMIN_ROLE role

CACHE_MANAGER

Detach a list of nodes from a cache grid:

- Call the ttGridDetachList built-in procedure.

- CREATE SESSION

- TT_CACHE_ADMIN_ROLE role

CACHE_MANAGER

Destroy a cache grid:

- Call the ttGridDestroy built-in procedure.

- CREATE SESSION

- TT_CACHE_ADMIN_ROLE role

CACHE_MANAGER

Start the cache agent with either:

- Call the ttCacheStart built-in procedure.

- Run the ttAdmin -cacheStart utility command.

CREATE SESSION

CACHE_MANAGER

Stop the cache agent

- Call the ttCacheStop built-in procedure

- Run the ttAdmin -cacheStop utility command

None

CACHE_MANAGER

Set a cache agent start policy with either:

- Call the ttCachePolicySet built-in procedure.

- Run the ttAdmin -cachePolicy utility command.

CREATE SESSIONFoot 5

CACHE_MANAGER

Return the cache agent start policy setting:

- Call the ttCachePolicyGet built-in procedure.

CREATE SESSION

None

Start the replication agent with either:

- Call the ttRepStart built-in procedure.

- Run the ttAdmin -repStart utility command.

None

CACHE_MANAGER

Stop the replication agent with either:

- Call the ttRepStop built-in procedure.

- Run the ttAdmin -repStop utility command.

None

CACHE_MANAGER

Set a replication agent start policy

- Call the ttRepPolicySet built-in procedure

- Run the ttAdmin -repPolicy utility command

None

ADMIN

CREATE ACTIVE STANDBY PAIR with INCLUDE CACHE GROUP

when the cache group created is an AWT cache group

CREATE TRIGGER

Duplicate the database with ttRepAdmin -duplicate when using an AWT cache group within an active standby pair replication scheme

CREATE TRIGGER

CREATE [DYNAMIC] READONLY CACHE GROUP with AUTOREFRESH MODE INCREMENTAL

- CREATE SESSION

- SELECT ON table_nameFoot 6

- RESOURCEFootref 4

- CREATE ANY TRIGGERFootref 4

- CREATE [ANY] CACHE GROUPFoot 7

- CREATE [ANY] TABLEFoot 8

CREATE [DYNAMIC] READONLY CACHE GROUP with AUTOREFRESH MODE FULL

- CREATE SESSION

- SELECT ON table_nameFootref 6

- CREATE [ANY] CACHE GROUPFootref 7

- CREATE [ANY] TABLEFootref 8

CREATE [DYNAMIC] ASYNCHRONOUS WRITETHROUGH [GLOBAL] CACHE GROUP

- CREATE SESSION

- SELECT ON table_nameFootref 6

- RESOURCEFootref 4

- CREATE [ANY] CACHE GROUPFootref 7

- CREATE [ANY] TABLEFootref 8

CREATE [DYNAMIC] SYNCHRONOUS WRITETHROUGH CACHE GROUP

- CREATE SESSION

- SELECT ON table_nameFootref 6

- CREATE [ANY] CACHE GROUPFootref 7

- CREATE [ANY] TABLEFootref 8

CREATE [DYNAMIC] USERMANAGED CACHE GROUP

(see variants in following rows)

- CREATE SESSION

- SELECT ON table_nameFootref 6

- CREATE [ANY] CACHE GROUPFootref 7

- CREATE [ANY] TABLEFootref 8

CREATE [DYNAMIC] USERMANAGED CACHE GROUP with AUTOREFRESH MODE INCREMENTAL

- CREATE SESSION

- SELECT ON table_nameFootref 6

- RESOURCEFootref 4

- CREATE ANY TRIGGERFootref 4

- CREATE [ANY] CACHE GROUPFootref 7

- CREATE [ANY] TABLEFootref 8

CREATE [DYNAMIC] USERMANAGED CACHE GROUP with AUTOREFRESH MODE FULL

- CREATE SESSION

- SELECT ON table_nameFootref 6

- CREATE [ANY] CACHE GROUPFootref 7

- CREATE [ANY] TABLEFootref 8

CREATE [DYNAMIC] USERMANAGED CACHE GROUP with READONLY

- CREATE SESSION

- SELECT ON table_nameFootref 6

- CREATE [ANY] CACHE GROUPFootref 7

- CREATE [ANY] TABLEFootref 8

CREATE [DYNAMIC] USERMANAGED CACHE GROUP with PROPAGATE

- CREATE SESSION

- SELECT ON table_nameFootref 6

- CREATE [ANY] CACHE GROUPFootref 7

- CREATE [ANY] TABLEFootref 8

ALTER CACHE GROUP SET AUTOREFRESH STATE PAUSED

- CREATE SESSION

- SELECT ON table_nameFootref 6,Foot 9

- RESOURCEFootref 4, Footref 9

- CREATE ANY TRIGGERFootref 4 ,Footref 9

ALTER ANY CACHE GROUPFoot 10

ALTER CACHE GROUP SET AUTOREFRESH STATE ON

- CREATE SESSION

- SELECT ON table_nameFootref 6, Footref 9

- RESOURCEFootref 4, Footref 9

- CREATE ANY TRIGGERFootref 4, Footref 9

ALTER ANY CACHE GROUPFootref 10

ALTER CACHE GROUP SET AUTOREFRESH STATE OFF

CREATE SESSION

ALTER ANY CACHE GROUPFootref 10

ALTER CACHE GROUP SET AUTOREFRESH MODE FULL

CREATE SESSION

ALTER ANY CACHE GROUPFootref 10

ALTER CACHE GROUP SET AUTOREFRESH MODE INCREMENTAL

- CREATE SESSION

- SELECT ON table_nameFootref 6

- RESOURCEFootref 4

- CREATE ANY TRIGGERFootref 4

ALTER ANY CACHE GROUPFootref 10

ALTER CACHE GROUP SET AUTOREFRESH INTERVAL

- CREATE SESSION

- SELECT ON table_nameFootref 6, Foot 11

ALTER ANY CACHE GROUPFootref 10

LOAD CACHE GROUP

- CREATE SESSION

- SELECT ON table_nameFootref 6

LOAD {ANY CACHE GROUP | ON cache_group_name)Footref 10

REFRESH CACHE GROUP

- CREATE SESSION

- SELECT ON table_nameFootref 6

REFRESH {ANY CACHE GROUP | ON cache_group_name)Footref 10

FLUSH CACHE GROUP

- CREATE SESSION

- UPDATE ON table_nameFootref 6

- INSERT ON table_nameFootref 6

FLUSH {ANY CACHE GROUP | ON cache_group_name)Footref 10

UNLOAD CACHE GROUP

None

UNLOAD {ANY CACHE GROUP | ON cache_group_name)Footref 10

DROP CACHE GROUP

CREATE SESSION

- DROP ANY CACHE GROUPFootref 10

- DROP ANY TABLEFoot 12

Synchronous writethrough or propagate

- CREATE SESSION

- INSERT ON table_nameFootref 6, Foot 13

- UPDATE ON table_nameFootref 6, Footref 13

- DELETE ON table_nameFootref 6, Footref 13

- INSERT ON table_nameFoot 14

- UPDATE ON table_nameFootref 14

- DELETE ON table_nameFootref 14

Asynchronous writethrough

- CREATE SESSION

- INSERT ON table_nameFootref 6

- UPDATE ON table_nameFootref 6

- DELETE ON table_nameFootref 6

- INSERT ON table_nameFootref 14

- UPDATE ON table_nameFootref 14

- DELETE ON table_nameFootref 14

Asynchronous writethrough when the CacheAWTMethod connection attribute is set to 1

CREATE PROCEDURE

Note: This privilege is an addition to the privileges needed for any asynchronous writethrough cache group.

No additional privileges

Asynchronous writethrough cache for Oracle Database CLOB, BLOB and NCLOB fields when the CacheAWTMethod connection attribute is set to 1

EXECUTE privilege on the Oracle Database DBMS_LOB PL/SQL package

Note: This privilege is an addition to the privileges needed for any asynchronous writethrough cache group.

No additional privileges

Incremental autorefresh

SELECT ON table_nameFootref 6

None

Full autorefresh

SELECT ON table_nameFootref 6

None

Dynamic load

- CREATE SESSION

- SELECT ON table_nameFootref 6

- SELECT ON table_nameFootref 14

- UPDATE ON table_nameFootref 14

- DELETE ON table_nameFootref 14

- INSERT ON table_nameFootref 14

Aging

None

DELETE {ANY TABLE | ON table_name)Footref 14

Set the LRU aging attributes

- Call the ttAgingLRUConfig built-in procedure

None

ADMIN

Generate Oracle Database SQL statements to manually install or uninstall Oracle Database objects

- Run the ttIsql utility's cachesqlget command

- Call the ttCacheSQLGet built-in procedure

CREATE SESSION

CACHE_MANAGER

Disable or enable propagation of committed cache table updates to the Oracle database

- Call the ttCachePropagateFlagSet built-in procedure

None

CACHE_MANAGER

Configure cache agent timeout and recovery method for autorefresh cache groups

- Call the ttCacheConfig built-in procedure

CREATE SESSION

CACHE_MANAGER

Set the AWT transaction log file threshold

- Call the ttCacheAWTThresholdSet built-in procedure

None

CACHE_MANAGER

Enable or disable monitoring of AWT cache groups

- Call the ttCacheAWTMonitorConfig built-in procedure

None

CACHE_MANAGER

Enable or disable tracking of DDL statements issued on cached Oracle Database tables

- Call the ttCacheDDLTrackingConfig built-in procedure

CREATE SESSION

CACHE_MANAGER

Return information about cache grids

- Call the ttGridInfo built-in procedure

- CREATE SESSION

- TT_CACHE_ADMIN_ROLE role

CACHE_MANAGER

Return information about cache grid nodes

- Call the ttGridNodeStatus built-in procedure

- CREATE SESSION

- TT_CACHE_ADMIN_ROLE role

CACHE_MANAGER

Footnote 1 At minimum, the cache administration user must have the CREATE TYPE privilege.

Footnote 2 At minimum, the cache manager user must have the CREATE SESSION privilege.

Footnote 3 If the cache administration user will not create autorefresh cache groups, then you can grant the CREATE TRIGGER privilege instead of the CREATE ANY TRIGGER privilege.

Footnote 4 Not required if the Oracle Database objects used to manage the caching of Oracle Database data are manually created with the initCacheAdminSchema.sql script.

Footnote 5 Required if the cache agent start policy is being set to always or norestart.

Footnote 6 Required on all Oracle Database tables cached in the TimesTen cache group except for tables owned by the cache administration user.

Footnote 7 The CACHE_MANAGER privilege includes the CREATE [ANY] CACHE GROUP privilege. ANY is required if the cache manager user creates cache groups owned by a user other than itself.

Footnote 8 ANY is required if any of the cache tables are owned by a user other than the cache manager user.

Footnote 9 Required if the cache group's autorefresh mode is incremental and initial autorefresh state is OFF, and the Oracle Database objects used to manage the caching of Oracle Database data are automatically created.

Footnote 10 Required if the TimesTen user accessing the cache group does not own the cache group.

Footnote 11 Required if the cache group's autorefresh mode is incremental.

Footnote 12 Required if the TimesTen user accessing the cache group does not own all its cache tables.

Footnote 13 The privilege must be granted to the Oracle Database user with the same name as the TimesTen cache manager user if the Oracle Database user is not the cache administration user.

Footnote 14 Required if the TimesTen user accessing the cache table does not own the table.

B SQL*Plus Scripts for TimesTen Application-Tier Database Cache

This appendix lists the SQL*Plus scripts that are installed with TimesTen Application-Tier Database Cache used to perform various configuration, administrative and monitoring tasks, and provides links to more information including examples. All scripts are installed in the TimesTen_install_dir/oraclescripts directory.

Installed SQL*Plus scripts

- cacheCleanUp.sql: Drops Oracle Database objects such as change log tables and triggers used to implement autorefresh operations. Script is used when a TimesTen database containing autorefresh cache groups is unavailable because the TimesTen system is offline, or the database was destroyed without dropping its autorefresh cache groups. Run this script as the cache administration user. See "Dropping Oracle Database objects used by autorefresh cache groups" for more information.

- cacheInfo.sql: Returns change log table information for all Oracle Database tables cached in an autorefresh cache group, and information about Oracle Database objects used to track DDL statements issued on cached Oracle Database tables. Script is used to monitor autorefresh operations on cache groups and DDL statements issued on cached Oracle Database tables. Run this script as the cache administration user. See "Monitoring autorefresh operations on cache groups" and "Tracking DDL statements issued on cached Oracle Database tables" for more information.

- grantCacheAdminPrivileges.sql: Grants privileges to the cache administration user that are required to automatically create Oracle Database objects used to manage the caching of Oracle Database data when particular cache grid and cache group operations are performed. Run this script as the sys user. See "Automatically create Oracle Database objects used to manage data caching" for more information.

- initCacheAdminSchema.sql: Grants a minimal set of privileges to the cache administration user and manually creates Oracle Database objects used to manage the caching of Oracle Database data. Run this script as the sys user. See "Manually create Oracle Database objects used to manage data caching" for more information.

- initCacheGlobalSchema.sql: Creates the Oracle Database timesten user, the Oracle Database tables owned by the timesten user to store information about cache grids, and the TT_CACHE_ADMIN_ROLE role that defines privileges on these Oracle Database tables. Script must be run regardless of whether you are automatically or manually creating Oracle Database objects used to manage caching of Oracle Database data. Run this script as the sys user. See "Create the Oracle database users" for more information.

- initCacheGridSchema.sql: Manually creates Oracle Database tables used to store information about TimesTen databases that are associated with a particular cache grid. Run this script as the sys user. See "Manually create Oracle Database objects used to manage data caching" for more information.

- README: Contains descriptions of the SQL*Plus scripts that are installed with TimesTen Application-Tier Database Cache.

C Compatibility Between TimesTen and Oracle Databases

The following sections list compatibility issues between TimesTen and Oracle Databases. The list is not complete, but it indicates areas that require special attention.

- Summary of compatibility issues

- Transaction semantics

- API compatibility

- SQL compatibility

- Mappings between Oracle Database and TimesTen data types

Summary of compatibility issues

Consider the following differences between TimesTen and Oracle databases:

- TimesTen and Oracle database metadata are stored differently. See "API compatibility" for more information.

- TimesTen and Oracle databases have different transaction isolation models. See "Transaction semantics" for more information.

- TimesTen and Oracle databases have different connection and statement properties. For example, TimesTen does not support catalog names, scrollable cursors or updateable cursors.

- Sequences are not cached and synchronized between the TimesTen database and the corresponding Oracle database. See "SQL expressions" for more information.

- Side effects of Oracle Database triggers and stored procedures are not reflected in the TimesTen database until after an automatic or manual refresh operation.

Transaction semantics

TimesTen and Oracle Database transaction semantics differ as follows:

- Oracle Database serializable transactions can fail at commit time because the transaction cannot be serialized. TimesTen uses locking to enforce serializability.

- Oracle Database can provide both statement-level and transaction-level consistency by using a multiversion consistency model. TimesTen does not provide statement-level consistency. TimesTen provides transaction-level consistency by using serializable isolation.

- Oracle Database users can lock tables explicitly through SQL. This locking feature is not supported in TimesTen.

- Oracle Database supports savepoints while TimesTen does not.

- In Oracle Database, a transaction can be set to be read-only or read/write. This is not supported in TimesTen.

For more information about TimesTen isolation levels and transaction semantics, see "Transaction Management" in Oracle TimesTen In-Memory Database Operations Guide.

API compatibility

For a complete list of the JDBC API classes and interfaces that TimesTen supports with notes on which methods have a compatibility issue, see "Key JDBC classes and interfaces" in Oracle TimesTen In-Memory Database Java Developer's Guide.

For a complete list of the ODBC API functions that TimesTen supports with notes on which functions have a compatibility issue, see "TimesTen ODBC Functions and Options" in Oracle TimesTen In-Memory Database C Developer's Guide.

For a complete list of the OCI functions that TimesTen supports for Oracle database release 11.2.0.2, see "TimesTen Support for OCI" in Oracle TimesTen In-Memory Database C Developer's Guide.

For information about TimesTen support for Pro*C/C++, see "TimesTen Support for Oracle Pro*C/C++" in Oracle TimesTen In-Memory Database C Developer's Guide.

For information about TimesTen support for ODP.NET, see Oracle Data Provider for .NET Oracle TimesTen In-Memory Database Support User's Guide.

For information about TimesTen support for PL/SQL, see Oracle TimesTen In-Memory Database PL/SQL Developer's Guide.

The TimesTen C++ Interface Classes (TTClasses) library provides a high-performance interface to TimesTen that is easy to use. This C++ class library provides wrappers around the most common ODBC functionality. This API is not available for the Oracle Database. See Oracle TimesTen In-Memory Database TTClasses Guide.

SQL compatibility

This section compares TimesTen's SQL implementation with Oracle Database SQL. The purpose is to provide users with a list of Oracle Database SQL features not supported in TimesTen or supported with different semantics.

Schema objects

TimesTen does not recognize some of the schema objects that are supported in Oracle Database. TimesTen returns a syntax error when a statement manipulates or uses these objects. TimesTen passes the statement to Oracle Database. The unsupported objects are:

Clusters
Objects created by the CREATE DATABASE statement
Objects created by the CREATE JAVA statement
Database links
Database triggers
Dimensions
Extended features
External procedure libraries
Index-organized tables
Mining models
Partitions
Object tables, types and views
Operators

TimesTen supports views and materialized views, but it cannot cache an Oracle Database view. TimesTen can cache an Oracle Database materialized view in a user managed cache group without the AUTOREFRESH cache group attribute and PROPAGATE cache table attribute. The cache group must be manually loaded and flushed.

Caching Oracle Database partitioned tables

TimesTen can cache Oracle Database partitioned tables at the table level, but individual partitions cannot be cached. The following describes how operations on partitioned tables affect cache groups:

- DDL operations on a table that has partitions do not affect the cache group unless there is data loss. For example, if a partition with data is truncated, an AUTOREFRESH operation does not delete the data from the corresponding cached table.

- WHERE clauses in any cache group operations cannot reference individual partitions or subpartitions. Any attempt to define a single partition of a table returns an error.

Nonschema objects

TimesTen does not recognize some of the schema objects that are supported in Oracle Database. TimesTen returns a syntax error when a statement manipulates or uses these objects. TimesTen passes the statement to Oracle Database. The unsupported objects are:

Contexts
Directories
Editions
Restore points
Roles
Rollback segments
Tablespaces

Differences between Oracle Database and TimesTen tables

The Oracle Database table features that TimesTen does not support are:

- ON DELETE SET NULL

- Check constraints

- Foreign keys that reference the table on which they are defined

Data type support

The following Oracle Database data types are not supported by TimesTen:

TIMESTAMP WITH TIME ZONE
TIMESTAMP WITH LOCAL TIME ZONE
INTERVAL YEAR TO MONTH
INTERVAL DAY TO SECOND
UROWID
BFILE
Oracle Database-supplied types
User-defined types

The following TimesTen data types are not supported by Oracle Database:

TT_CHAR
TT_VARCHAR
TT_NCHAR
TT_NVARCHAR
TT_BINARY
TT_VARBINARY
TINYINT and TT_TINYINT
TT_SMALLINT
TT_INTEGER
TT_BIGINT
TT_DECIMAL
TT_DATE
TIME and TT_TIME
TT_TIMESTAMP

Note:
TimesTen NCHAR and NVARCHAR2 data types are encoded as UTF-16. Oracle Database NCHAR and NVARCHAR2 data types are encoded as either UTF-16 or UTF-8.
To cache an Oracle Database NCHAR or NVARCHAR2 column, the Oracle Database NLS_NCHAR_CHARACTERSET encoding must be AL16UTF16, not AL32UTF8.

SQL operators

TimesTen supports these operators and predicates that are supported by Oracle Database:

unary -
+, -, *, /
=, <, >, <=, >=, <>, !=
||
IS NULL, IS NOT NULL
LIKE (Oracle Database LIKE operator ignores trailing spaces, but TimesTen does not)
BETWEEN
IN
NOT IN (list)
AND
OR
+ (outer join)
ANY, SOME
ALL (list)
EXISTS
UNION
MINUS
INTERSECT

To perform a bitwise AND operation of two bit vector expressions, TimesTen uses the ampersand character (&) between the expressions while Oracle Database uses the BITAND function with the expressions as arguments.

SELECT statements

TimesTen supports these clauses of a SELECT statement that are supported by Oracle Database:

- FOR UPDATE

- ORDER BY, including NULLS FIRST and NULLS LAST

- GROUP BY, including ROLLUP, GROUPING_SETS and grouping expression lists

- Table alias

- Column alias

- Subquery factoring clause with constructor

Oracle Database supports flashback queries, which are queries against a database that is in some previous state (for example, a query on a table as of yesterday). TimesTen does not support flashback queries.

TimesTen does not support the CONNECT BY clause.

SQL subqueries

TimesTen supports these subqueries that are supported by Oracle Database:

IN (subquery)
>,<,= ANY (subquery)
>,=,< SOME (subquery)
EXISTS (subquery)
>,=,< (scalar subquery)
Subqueries in WHERE clause of DELETE/UPDATE
Subqueries in FROM clause
Subquery factoring clause (WITH constructor)

Note:
A nonverifiable scalar subquery is a scalar subquery whose 'single-row-result-set' property cannot be determined until execution time. TimesTen allows at most one nonverifiable scalar subquery in the entire query and the subquery cannot be specified in an OR expression.

SQL functions

TimesTen supports these functions that are supported by Oracle Database:

ABS
ADD_MONTHS
ASCIISTR
AVG
CAST
CEIL
COALESCE
CONCAT
COUNT
CHR
DECODE
DENSE_RANK
EMPTY_BLOB
EMPTY_CLOB
EXTRACT
FIRST_VALUE
FLOOR
GREATEST
GROUP_ID
GROUPING
GROUPING_ID
INSTR
LAST_VALUE
LEAST
LENGTH
LOWER
LPAD
LTRIM
MAX
MIN
MOD
MONTHS_BETWEEN
NCHR
NLS_CHARSET
NLS_CHARSET_NAME
NLSSORT
NULLIF
NUMTOYMINTERVAL
NUMTODSINTERVAL
NVL
POWER
RANK
REPLACE
ROUND
ROW_NUMBER
RPAD
RTRIM
SIGN
SQRT
SUBSTR
SUM
SYS_CONTEXT
SYSDATE
TO_BLOB
TO_CLOB
TO_CHAR
TO_DATE
TO_LOB
TO_NCLOB
TO_NUMBER
TRIM
TRUNC
UID
UNISTR
UPPER
USER

These TimesTen functions are not supported by Oracle Database:

CURRENT_USER
GETDATE
ORA_SYSDATE
SESSION_USER
SYSTEM_USER
TIMESTAMPADD
TIMESTAMPDIFF
TT_HASH
TT_SYSDATE
TTGRIDNODENAME
TTGRIDMEMBERID
TTGRIDUSERASSIGNEDNAME

TimesTen and the Oracle Database interpret the literal N'\UNNNN' differently. In TimesTen, N'\unnnn' (where nnnn is a number) is interpreted as the national character set character with the code nnnn. In the Oracle Database, N'\unnnn' is interpreted as 6 literal characters. The \u is not treated as an escape. This difference causes unexpected behavior. For example, loading a cache group with a WHERE clause that contains a literal can fail. This can also affects dynamic loading and cache grid operation. Applications should use the UNISTR SQL function instead of literals.

SQL expressions

TimesTen supports these expressions that are supported by Oracle Database:

Column Reference
Sequence
NULL
()
Binding parameters
CASE expression
ROWID pseudocolumn
ROWNUM pseudocolumn

TimesTen and Oracle Database treat literals differently. See the description of HexadecimalLiteral in "Constants" in Oracle TimesTen In-Memory Database SQL Reference.

INSERT/DELETE/UPDATE/MERGE statements

TimesTen supports these DML statements that are supported by Oracle Database:

- INSERT INTO ... VALUES

- INSERT INTO ... SELECT

- UPDATE WHERE expression (expression may contain a subquery)

- DELETE WHERE expression (expression may contain a subquery)

TimesTen does not support updating of primary key values except when the new value is the same as the old value.

TimesTen-only SQL and built-in procedures

This section lists TimesTen SQL statements and functions and built-in procedures that are not supported by Oracle Database. With PassThrough=3, these statements are passed to Oracle Database for execution and an error is generated.

- All TimesTen cache group DDL and DML statements, including CREATE CACHE GROUP, DROP CACHE GROUP, ALTER CACHE GROUP, LOAD CACHE GROUP, UNLOAD CACHE GROUP, REFRESH CACHE GROUP and FLUSH CACHE GROUP.

- All TimesTen replication management DDL statements, including CREATE REPLICATION, DROP REPLICATION, ALTER REPLICATION, CREATE ACTIVE STANDBY PAIR, ALTER ACTIVE STANDBY PAIR and DROP ACTIVE STANDBY PAIR.

- FIRST n clause.

- ROWS m TO n clause.

- All TimesTen built-in procedures. See "Built-In Procedures" in Oracle TimesTen In-Memory Database Reference.

PL/SQL constructs

TimesTen supports a subset of stored procedure constructs, functions, data types, packages and package bodies that are supported by Oracle Database. See Oracle TimesTen In-Memory Database PL/SQL Developer's Guide for details.

Mappings between Oracle Database and TimesTen data types

When you choose data types for columns in the TimesTen cache tables, consider the data types of the columns in the Oracle Database tables and choose an equivalent or compatible data type for the columns in the cache tables.

Note:
TimeTen cache, including passthrough, does not support the Oracle Database ROWID data type. However, you can cast a ROWID data type to a CHAR(18) when provided on the SELECT list in a SQL query.
The following example demonstrates the error that is returned when you do not cast the ROWID data type. Then, the example shows the correct casting of a ROWID data type to CHAR(18):

Command> SET PASSTHROUGH 3;
Passthrough command has set autocommit off.
Command> SELECT ROWID FROM dual;
5115: Unsupported type mapping for column ROWID
The command failed.
Command> SELECT CAST (ROWID AS CHAR(18)) FROM DUAL;
< AAAAB0AABAAAAEoAAA >
1 row found.

Primary and foreign key columns are distinguished from non-key columns. The data type mappings allowed for key columns in a cache table are shown in Table C-1.

Table C-1 Data type mappings allowed for key columns

Oracle Database data type

TimesTen data type

NUMBER(p,s)

NUMBER(p,s)

Note: DECIMAL(p,s) or NUMERIC(p,s) can also be used. They are aliases for NUMBER(p,s).

NUMBER(p,0)

INTEGER

TT_TINYINT

TT_SMALLINT

TT_INTEGER

TT_BIGINT

NUMBER(p,0)

NUMBER

TT_TINYINT

TT_SMALLINT

TT_INTEGER

TT_BIGINT

NUMBER

CHAR(m)

CHAR(m)

VARCHAR2(m)

VARCHAR2(m)

RAW(m)

VARBINARY(m)

DATE

DATE

TIMESTAMP(m)

TIMESTAMP(m)

NCHAR(m)

NCHAR(m)

NVARCHAR2(m)

NVARCHAR2(m)

Table C-2 shows the data type mappings allowed for non-key columns in a cache table.

Table C-2 Data type mappings allowed for non-key columns

Oracle Database data type

TimesTen data type

NUMBER(p,s)

NUMBER(p,s)

REAL

FLOAT

BINARY_FLOAT

DOUBLE

BINARY_DOUBLE

NUMBER(p,0)

INTEGER

TT_TINYINT

TT_SMALLINT

TT_INTEGER

TT_BIGINT

NUMBER(p,0)

FLOAT

BINARY_FLOAT

DOUBLE

BINARY_DOUBLE

NUMBER

TT_TINYINT

TT_SMALLINT

TT_INTEGER

TT_BIGINT

NUMBER

REAL

FLOAT

BINARY_FLOAT

DOUBLE

BINARY_DOUBLE

CHAR(m)

CHAR(m)

VARCHAR2(m)

VARCHAR2(m)

RAW(m)

VARBINARY(m)

LONG

VARCHAR2(m)

Note: m can be any valid value within the range defined for the VARCHAR2 data type.

LONG RAW

VARBINARY(m)

Note: m can be any valid value within the range defined for the VARBINARY data type.

DATE

DATE

TIMESTAMP(0)

TIMESTAMP(m)

TIMESTAMP(m)

FLOAT(n)

Note: Includes DOUBLE and FLOAT, which are equivalent to FLOAT(126). Also includes REAL, which is equivalent to FLOAT(63).

FLOAT(n)

BINARY_DOUBLE

Note: FLOAT(126) can be declared as DOUBLE. FLOAT(63) can be declared as REAL.

BINARY_FLOAT

BINARY_FLOAT

BINARY_DOUBLE

BINARY_DOUBLE

NCHAR(m)

NCHAR(m)

NVARCHAR2(m)

NVARCHAR2(m)

CLOB

VARCHAR2(n)

Note: 1<=m<=4 megabytes.

BLOB

VARBINARY(m)

Note: 1<=m<=16 megabytes.

NCLOB

NVARCHAR2(m)

Note: 1<=m<=4 megabytes.

Glossary

aging

Delete cache instances from the cache tables of a cache group after a specified period of time (time-based) or when a specified level of database usage is reached (LRU).

asynchronous writethrough (AWT) cache group

A cache group in which committed updates on TimesTen cache tables are automatically and asynchronously propagated to the cached Oracle Database tables. The commit on the TimesTen database occurs asynchronously from the commit on the Oracle database.

automatic refresh

Committed updates on cached Oracle Database tables are automatically refreshed to the TimesTen cache tables.

autorefresh cache group

A read-only cache group or a user managed cache group that uses the AUTOREFRESH MODE INCREMENTAL cache group attribute.

bidirectional transmit

Propagate committed updates on TimesTen cache tables to the cached Oracle Database tables, and refresh committed updates on cached Oracle Database tables to the TimesTen cache tables.

cache administration user

Oracle Database user that creates and maintains Oracle Database objects that store information used to manage cache grids and enforce predefined behaviors of particular cache group types.

cache agent

A TimesTen process that processes cache group operations, such as automatic refresh, loading a cache group, and passing through statements to the Oracle database for execution.

cache group

Defines the data from the Oracle Database tables to cache in a TimesTen database. A cache group can cache all or a subset of a single Oracle Database table or a set of related Oracle Database tables. If multiple Oracle Database tables are cached, each cache table (except for the root table) must reference another cache table in the cache group through foreign key constraints.

cache grid

A set of distributed grid members consisting of TimesTen in-memory databases that work together to cache data from a single Oracle database and guarantee cache coherence among the TimesTen databases.

cache group primary key

The primary key of the cache group's root table.

cache instance

A specific row of data identified by the primary key in the cache group's root table. If there are multiple tables in the cache group, the cache instance consists of the set of rows in the child tables associated by foreign key relationships with the row in the root table.

cache manager user

TimesTen user that performs cache grid and cache group operations such as creating and configuring a cache grid, and creating cache groups.

cache table

The root table or a child table in a cache group.

cache table users

TimesTen users who own cache tables.

child table

A cache table that has a foreign key reference to either the primary key of the root table or another child table that either directly or indirectly references the root table. The table hierarchy in your cache group can designate child tables to be parents of other child tables. No cache table can be a child to more than one parent in the cache group.

dynamic cache group

A cache group category for which data in its cache tables can be loaded on demand, manually loaded or automatically loaded.

dynamic load

The transfer of data into the local grid member from Oracle Database tables when a query cannot be satisfied with data in the cache grid members.

explicitly loaded cache group

A cache group category for which data in its cache tables are manually or automatically loaded.

flush

To manually propagate committed inserts or updates on TimesTen cache tables in a user managed cache group to the cached Oracle Database tables.

global cache group

A cache group classification where data in its cache tables are shared across multiple TimesTen databases within a cache grid.

grid data transfer

Transfer of the cache instance from remote grid members to the local grid member in response to a query that cannot be satisfied by data in the cache tables on the local grid member.

grid member

A component of a cache grid consisting of either a standalone TimesTen database or an active standby pair.

grid node

A TimesTen database of a grid member that is either a standalone database, or the active database or standby database of an active standby pair.

load

Copy new cache instances from the cached Oracle Database tables to the TimesTen cache tables. Cache instances that are already exist in the cache tables are not updated or deleted.

local cache group

A cache group classification where data in its cache tables are not shared across multiple TimesTen databases even if the databases are members of the same cache grid.

Oracle Database schema users

Oracle Database users who own Oracle Database tables to be cached in a TimesTen database.

Oracle Database timesten user

Oracle Database user who owns Oracle Database tables that store information about cache grids.

propagate

Transmit committed updates on TimesTen cache tables to the cached Oracle Database tables.

read-only cache group

A cache group in which committed updates on cached Oracle Database tables are automatically refreshed to the TimesTen cache tables. You cannot update cache tables directly in a read-only cache group.

refresh

For an explicitly loaded cache group, unload and then load the cache group.

For a dynamic cache group, replace existing cache instances in the cache tables with the most current data from the cached Oracle Database tables.

replication

The process of maintaining duplicate copies of data in multiple databases.

replication agent

Replication at each master and subscriber TimesTen database is controlled by a replication agent process. The replication agent on the master database reads the transaction log records and transmits any committed updates on replicated elements to the replication agent on the subscriber database. The replication agent on the subscriber database then applies the updates to its database.

For an AWT cache group, the replication agent transmits committed updates on its cache tables to the cached Oracle Database tables.

root table

The parent table in the cache group that does not reference any other table in the cache group through a foreign key constraint. The primary key of the root table is the primary key of the cache group.

synchronous writethrough (SWT) cache group

A cache group in which committed updates on TimesTen cache tables are automatically and synchronously propagated to the cached Oracle Database tables. When an application commits a transaction, it is committed on Oracle Database before it is committed on TimesTen.

system managed cache group

System managed cache groups enforce predefined behaviors. The types of system managed cache groups are read-only, synchronous writethrough and asynchronous writethrough.

TT_CACHE_ADMIN_ROLE role

Role granted to the cache administration user that defines privileges on the Oracle Database tables owned by the timesten user which store information about cache grids.

user managed cache group

A cache group that implements customized behavior such as bidirectional transmit.

unload

Delete cache instances from a cache table. The rows in the cached Oracle Database tables are not affected.

Index
A  B  C  D  E  F  G  H  I  L  M  N  O  P  Q  R  S  T  U  V  W

A

active standby pair

active database, 6.2.1

create, 6.2.1

definition, 6.2

read-only subscriber database, 6.2.3

standby database, 6.2.2

AgentFailoverTimeout parameter, 11.3 aging policy

cache group, 4.5

LRU aging, 4.5.1

time-based aging, 4.5.2

asynchronous writethrough cache group, see AWT cache group autocommit

global queries, 6.4, 6.4.1

autorefresh

cleanup

drop Oracle Database objects, 7.5

definition, 1.2.3 example, 2.5.2 incremental

avoid transactional inconsistency, 8.3.1.2

initiate, 4.2.5, 5.2.4 interval, 4.2.5 mode, 4.2.5 select limit, 8.3.2 state, 4.2.5 statistics, 8.5 status, 7.4 autorefresh cache group

change log table, 7.4

defragment, 7.6.1

definition, 3.2.1 load and refresh, 5.2.1 manually create Oracle Database objects, 4.2.5.2 monitoring, 7.2.2 read-only

performance, 8.3.1, 8.3.2

recovery method, 7.4 status, 7.4 transaction reclaim performance, 8.4 AUTOREFRESH cache group attribute, 4.2.5 AWT cache group

create, 2.3.3, 4.2.2

definition, 1.2.2, 4.2.2

error reporting, 4.2.2.3, 4.2.2.5

monitoring, 7.2.3

parallel propagation, 4.2.2.2, 8.2.1

batch size, 4.2.2.2.3

restrictions, 4.2.2.4 awterrs file, 4.2.2.3, 4.2.2.5

DTD for XML format, 4.2.2.5

XML format, 4.2.2.5

B

BLOB data

caching in TimesTen, 4.4

built-in procedures

ttAgingLRUConfig, 4.5.1

ttAgingScheduleNow, 4.5.3

ttCacheAWTMonitorConfig, 7.2.3

ttCacheAWTThresholdSet, 7.2.4

ttCacheConfig, 7.4

AgentTimeout parameter, 7.4

AutoRefreshLogTblSpaceUsagePCT parameter, 7.6.2

TblSpaceFullRecovery parameter, 7.6.3

ttCacheDbCgStatus, 7.4 ttCacheDDLTrackingConfig, 7.2.7, 7.2.7 ttCachePolicySet, 3.6.1 ttCacheStart, 2.3.2, 3.6 ttCacheStop, 2.7.5, 3.6, 9.5 ttCacheUidGet, 3.5 ttCacheUidPwdSet, 2.1.4, 3.3.4 ttGridAttach, 2.4, 3.6.1, 4.7.4 ttGridCreate, 2.2, 3.4.2.2 ttGridDestroy, 2.7.4, 9.4 ttGridDetach, 2.7.1, 9.1 ttGridDetachList, 9.1 ttGridInfo, 7.2.5 ttGridNameSet, 2.2, 3.4.2.3 ttGridNodeStatus, 7.2.5 ttRepPolicySet, 4.2.2.1 ttRepStart, 2.3.4, 4.2.2.1 ttRepStateGet, 7.7 ttRepStateSet, 6.2.1 ttRepStop, 2.7.2, 4.2.2.1, 9.2, 9.2 ttRepSubscriberWait, 7.2.7, 9.3

C

cache

manage, 3.2.3, 3.2.4

manage through Oracle Database object, 3.2.4

performance evaluation, 10.1

cache administration user

caching table on more than one TimesTen database, 8.6

create, 2.1.1, 3.2.1, 10.2.1

default tablespace

create, 2.1.1, 3.2.1, 10.2.1

drop, 2.7.6, 9.7, 10.6.1, 10.6.2

monitoring, 7.6

recover when full, 7.6.3

usage warning threshold, 7.6.2

definition, 2.1.1, 3.2.1 determine, 3.5 set in TimesTen database, 2.1.4, 3.3.4 Cache Advisor

configuration, 10.2

configure repository database, 10.2.2

configure target Oracle database, 10.2.1

configure TimesTen database, 10.2.3

DataPump, 10.4.1

executing, 10.4

-export option, 10.4.1

-ftp option, 10.4.1

identify target Oracle database, 10.4

-import option, 10.4.1

-OraDirNfs option, 10.4.1

overview, 10

performance option, 10.4.1

post-processing clean up, 10.6

recommends cache group definitions, 10.1

repository setup script, 10.2.2

supported configurations, 10.2.4

target

setup script, 10.2.1

usage guidelines, 10.2.4 cache agent

connection failure, 7.1.1

reconnecting with Oracle Database, 11.1

start, 2.3.2, 3.6

start policy

and cache grid, 3.6.1

definition, 3.6.1

set, 3.6.1

status, 7.1, 7.1 stop, 2.7.5, 3.6, 9.5 timeout, 7.4 cache grid

associate TimesTen database, 2.2, 3.4.2.3

attach a TimesTen database, 2.4, 4.7.4

cache agent

start policy, 3.6.1, 3.6.1

cache agent start policy, 7.7 create, 2.2, 3.4.2.2 data transfer, 4.7.1, 4.7.2 definition, 1.1, 1.1.1, 3.4, 3.4.2 destroy, 2.7.4, 9.4 detach

set of TimesTen databases, 9.1

TimesTen database, 2.7.1, 9.1

failure, 7.7 global query with local join, 6.4.1 instance owner, 4.7.1 location of data, 6.4.2 member

attach, 7.7

definition, 1.1.1, 3.4.2

detach all, 9.1

port, 4.7.4

sharing data, 6.3

member failure, 3.6.1 node

definition, 1.1.1, 3.4.2

Oracle Database system parameters, 3.4.2.1 recovery, 7.7 ten or more nodes, 3.4.2.1 using ttRepStateGet, 7.7, 7.7 cache group

autorefresh

definition, 1.2.3, 3.2.1

large transactions, 8.3.1

transaction reclaim performance, 8.4

create, 2.3 dead

recovery, 7.4

definition, 1.2, 4.1 dynamic load, 5.3 flush

definition, 1.2.3

load, 1.2.3 read-only

autorefresh, 8.3.2

improving autorefresh, 8.3.1, 8.3.2

recommendations

Cache Advisor, 10.1

refresh, 1.2.3 table hierarchy, 4.1.2 table partition, C.4.1.1 cache instance

definition, 1.2.1, 5.3

owner, 4.7.1

ownership, 4.7, 4.7.1

propagate

definition, 1.2.3

cache manager user

create, 2.1.3, 3.3.2, 10.2.3

defined, 3.3.2

definition, 2.1.3, 2.1.3, 3.3.2

minimum privileges, 2.1.3, 3.3.3, 10.2.3

cache table

caching on more than one TimesTen database, 8.6

ON DELETE CASCADE attribute, 4.2.7

PROPAGATE attribute, 4.2.4.2

READONLY attribute, 4.2.4.1

UNIQUE HASH ON attribute, 4.2.8

user

create, 2.1.3, 3.3.2

defined, 3.3.2

definition, 2.1.3, 3.3.2

CacheAWTMethod first connection attribute, 8.2 CacheAWTParallelism data store attribute, 3.3.1, 4.2.2.2 cacheCleanUp.sql SQL*Plus script, 7.5, B.1 CacheGridEnable connection attribute, 3.3.1, 3.4.1, 3.4.2.2 CacheGridMsgWait connection attribute, 4.7.1, 4.7.2 cachegroups ttIsql command, 2.3.3, 7.2.1 cacheInfo.sql SQL*Plus script, B.1 CacheParAwtBatchSize parameter, 4.2.2.2.3 cachesqlget ttIsql command, 4.2.5.2, 7.2.7 change log tables

defragment, 7.6.1

character set

on Oracle Database, 10.2.3

child table

definition, 1.2, 4.1.2

CLOB data

caching in TimesTen, 4.4

CONNECT BY clause, C.4.6 connection

between TimesTen and Oracle database, 3.5

failure

cache agent, 7.1.1

Oracle Database, 11.1

replication agent, 7.1.1

connection attributes

CacheGridEnable, 3.4.1, 3.4.2.2

CacheGridMsgWait, 4.7.1, 4.7.2

DatabaseCharacterSet, 3.3.1

DynamicLoadEnable, 5.3.1

DynamicLoadErrorMode, 5.3.4

LockLevel, 3.3.1

OracleNetServiceName, 3.3.1

OraclePWD, 3.3.1

PassThrough, 3.3.1, 5.7

PermSize, 3.3.1

PWD, 3.3.1

RACCallback, 11.3

TypeMode, 3.3.1

UID, 3.3.1

CREATE ACTIVE STANDBY PAIR statement, 6.2.1

D

Data Guard, 12.1

data store attributes

CacheAWTParallelism, 3.3.1

ReplicationApplyOrdering, 3.3.1

data type

differences between Oracle Database and TimesTen, C.4.4

mapping between Oracle Database and TimesTen, C.5

mapping for key columns, C.5

mapping for non-key columns, C.5

database

character set, 10.2.3

duplicate, 6.2.2

temporary, 4.2

DatabaseCharacterSet connection attribute, 3.3.1 DDL statements

tracking, 7.2.7

DeadDbRecovery parameter, 7.4, 7.4 DROP ACTIVE STANDBY PAIR statement

example, 9.3

DROP CACHE GROUP statement

example, 2.7.3, 9.3

DSN

Cache Advisor

TimesTen database, 10.2.3

TimesTen database

example, 2.1.2

DSN for TimesTen database

example, 3.3.1

duplicating a database, 6.2.2 dynamic cache group

create, 4.6

definition, 1.2.4, 4.6

dynamic global cache group

dynamic load, 4.7.1

dynamic load

configuration, 5.3.1

definition, 4.7.1, 5.3

disable, 5.3.1

display errors, 5.3.4

examples, 2.6.1, 5.3.3

guidelines, 5.3.2

rules, 5.3.2

DynamicLoadEnable connection attribute, 5.3.1, 5.3.1 DynamicLoadErrorMode connection attribute, 5.3.4

E

environment variables

Microsoft Windows, 3.1.2

UNIX, 3.1.1

explicitly loaded cache group

definition, 1.2.4

F

failure

cache grid member, 7.7

Fast Application Notification (FAN), 11.1 FLUSH CACHE GROUP statement

definition, 5.4

example, 5.4

foreign key

index, 4.2.2.2

restriction, 4.2.2.2

G

global cache group

definition, 1.2.5, 4.7

dynamic, 4.7.1

dynamic load, 5.3

example, dynamic, 4.7.1

example, explicitly loaded, 4.7.2

explicitly loaded, 4.7.2

ownership changes, 7.2.6

sharing data among grid members, 6.3

global query, 6.4

autocommit, 6.4, 6.4.1

local join, 6.4.1

global unload operation, 5.5.1 GlobalLocalJoin optimizer flag, 6.4.1 GlobalProcessing optimizer flag, 6.4 GlobalProcessing optimizer hint

unload operation, 5.5.1

grantCacheAdminPrivileges.sql script, 10.2.1, 10.2.1 grantCacheAdminPrivileges.sql SQL*Plus script, 2.1.1, 3.2.3, B.1 grid, see cache grid

H

high availability

active standby pair, 1.3

cache grid, 1.3

Data Guard, 1.3

Oracle Real Application Clusters (Oracle RAC), 1.3

I

index

foreign key, 4.2.2.2

initCacheAdminSchema.sql SQL*Plus script, 3.2.4, B.1 initCacheGlobalSchema.sql script, 10.2.1 initCacheGlobalSchema.sql SQL*Plus script, 2.1.1, 3.2.1, 10.2.1, 10.2.2, B.1 initCacheGridSchema.sql SQL*Plus script, 3.2.4, B.1 instance administrator, 2.1.3

L

LOAD CACHE GROUP statement

definition, 5.2

example, 2.5.1, 5.2, 5.2.8

PARALLEL clause, 5.2.6

WITH ID clause, 5.2.3

LOB data

cache administration user privileges, A.2

caching in TimesTen, 4.4

restrictions on caching, 4.4

local cache group

definition, 1.2.5

LockLevel connection attribute, 3.3.1 LRU aging policy, 4.5.1

M

materialized views

Oracle Database, 4.2.4, C.4.1

Maximum Availability Architecture (MAA), 12.1 multiple-table cache group, 4.1.2

N

NCLOB data

caching in TimesTen, 4.4

O

OCIAttrGet() OCI function

OCI_ATTR_ROW_COUNT option, 5.6

ON DELETE CASCADE cache table attribute, 4.2.7 Oracle Database

autorefresh

cleanup, 7.5

AWT errors, 4.2.2.5 character set

determine, 3.3.1

connection failures, 11.1 create objects to manage cache, 3.2.3 database character set

determine, 10.2.3

differences from TimesTen, C.1 execution errors, 4.2.2.5 manually manage cache, 3.2.4 objects to manage cache

determine, 3.2.4

tables and triggers, 7.3

partitioned tables, C.4.1.1 schema users

create, 2.1.1, 3.2.1, 10.2.1

definition, 3.2.1

Server releases

supported, 3.1

synonyms

cache, 4.3

user

cache administration user, 2.1.1

definition, 2.1.1

drop, 2.7.6, 9.7

privileges, 3.2.2, A.2

schema users, 2.1.1

users

timesten user, 3.2.1

Oracle RAC

using TimesTen Cache, 11.3

using TimesTen Cache in, 11.1

Oracle Real Application Clusters (Oracle RAC) Oracle SQL*Plus scripts

cacheCleanUp.sql, 7.5, B.1

cacheInfo.sql, B.1

grantCacheAdminPrivileges.sql, 2.1.1, 3.2.3, B.1

initCacheAdminSchema.sql, 3.2.4, B.1

initCacheGlobalSchema.sql, 2.1.1, 3.2.1, 10.2.1, 10.2.2, B.1

initCacheGridSchema.sql, 3.2.4, B.1

OracleNetServiceName connection attribute, 3.3.1 OraclePWD connection attribute, 3.3.1 owner

cache instance, 4.7.1

ownership

cache instance, 4.7, 4.7.1

P

parallel propagation

AWT cache group, 4.2.2.2, 8.2.1

foreign key

restriction, 4.2.2.2

restriction, 4.2.2.2.1 partition, C.4.1.1 PassThrough connection attribute, 3.3.1, 5.7

and RETURN TWOSAFE, 5.7

passthrough level

changing, 5.7.8

setting, 5.7

performance

Cache Advisor, 10.1

comparison between Oracle Database and TimesTen, 10.1

read-only cache group

incremental autorefresh, 8.3.2

large transactions, 8.3.1

transaction reclaim, 8.4 PermSize connection attribute, 3.3.1 port

cache grid member, 4.7.4

privileges

Oracle Database users, 3.2.2, A.2

propagate

cache instances

definition, 1.2.3

error reporting, 4.2.2.5 example, 2.6.2 parallel, 4.2.2.2, 8.2.1 PROPAGATE cache table attribute, 4.2.4.2 PWD connection attribute, 3.3.1

Q

query

cache grid, 6.4

global, 6.4

R

RACCallback connection attribute, 11.3

read-only cache group

autorefresh

performance, 8.3.1, 8.3.2

create, 2.3.3, 4.2.1 definition, 1.2.2, 4.2.1 incremental autorefresh

statistics, 8.5

large transactions, 8.3.1 restrictions, 4.2.1.1 READONLY cache table attribute, 4.2.4.1 refresh

autorefresh, 4.2.5

cache group, 1.2.3

initiate, 5.2.4

REFRESH CACHE GROUP statement

definition, 5.2

example, 5.2, 5.2.8

PARALLEL clause, 5.2.6

WITH ID clause, 5.2.3

replication agent

connection failure, 7.1.1

start, 2.3.4, 4.2.2.1

start policy

definition, 4.2.2.1

set, 4.2.2.1

status, 7.1, 7.1 stop, 2.7.2, 4.2.2.1, 9.2, 9.2 ReplicationApplyOrdering data store attribute, 3.3.1, 4.2.2.2 ReplicationParallelism data store attribute, 4.2.2.2 root table

definition, 1.2, 4.1.2

S

schema users

create, 2.1.1

definition, 2.1.1

scripts

SQL*Plus, B

TimesTen Cache, B

select limit, 8.3.2 SELECT statement

cache grid, 6.4

global, 6.4

semantics

differences between Oracle Database and TimesTen, C.2

single-table cache group, 4.1.1 sliding window

cache group, 4.5.4

SQL

differences between TimesTen and Oracle, C.4

SQLRowCount() ODBC function, 5.6 Statement.getUpdateCount() JDBC method, 5.6 synchronous writethrough (SWT) cache group

create, 4.2.3

definition, 1.2.2, 4.2.3

restrictions, 4.2.3.1

sys.odbc.ini

Cache Advisor

example, 10.2.3

system managed cache groups, 4.2

T

tables

caching on more than one TimesTen database, 8.6

Oracle Database, 7.3

partition, C.4.1.1

tablespace

create default, 2.1.1, 3.2.1, 10.2.1

defragmentation, 7.6.1

drop default, 2.7.6, 9.7, 10.6.1, 10.6.2

full, 7.6.3

monitoring default, 7.6

recover when full, 7.6.3, 7.6.3

threshold, 7.6.2, 7.6.2

usage notification, 7.6.2

utilization, 7.6.1

TAF

overview, 11.1

timeout, 11.3

TblSpaceFullRecovery parameter, 7.6.3 time-based aging policy, 4.5.2 TimesTen users

cache manager user, 2.1.3, 2.1.3, 3.3.2

cache table users, 2.1.3, 3.3.2

transaction

incremental autorefresh

performance, 8.3.1

large

incremental commit, 8.3.1

performance, 8.3.1

reclaim operations

performance, 8.4, 8.4

semantics

differences between Oracle Database and TimesTen, C.2

transaction log file threshold for AWT cache groups

set, 7.2.4

Transparent Application Failover (TAF), see TAF triggers

Oracle Database, 7.3

TT_CACHE_ADMIN_ROLE role

definition, 2.1.1, 3.2.1

drop, 2.7.6, 9.7, 10.6.1, 10.6.1

ttAdmin utility

-cachePolicy command, 3.6.1

-cacheStart command, 3.6

-cacheStop command, 3.6

-cacheUidGet command, 3.5

-cacheUidPwdSet command, 3.3.4

-query command, 7.1

-repPolicy command, 4.2.2.1

-repStart command, 4.2.2.1

-repStop command, 4.2.2.1

ttAgingLRUConfig built-in procedure, 4.5.1 ttAgingScheduleNow built-in procedure, 4.5.3 ttca_setupRepostory script, 10.2.2 ttCacheAdvisor utility

-oraConn option, 10.4

-oraDirObject option, 10.4

-oraTarget option, 10.4

usage, 10.4

ttCacheAutorefIntervalStatsGet built-in procedure, 8.5 ttCacheAutorefresh built-in procedure, 4.2.5, 5.2.4 ttCacheAutoRefreshLogDefrag built-in procedure

defragment tablespace, 7.6.1.1

ttCacheAutorefreshSelectLimit built-in procedure, 8.3.2 ttCacheAutorefreshStatsGet built-in procedure

tablespace

utilization, 7.6.1

ttCacheAutorefreshXactLimit built-in procedure, 8.3.1 ttCacheAWTMonitorConfig built-in procedure, 7.2.3 ttCacheAWTThresholdSet built-in procedure, 7.2.4 ttCacheConfig

usage notification, 7.6.2

ttCacheConfig built-in procedure

AgentFailoverTimeout parameter, 11.3

AgentTimeout parameter, 7.4

AutoRefreshLogTblSpaceUsagePCT parameter, 7.6.2

AwtErrrorXmlOutput, 4.2.2.5

DeadDbRecovery parameter, 7.4

defragment tablespace, 7.6.1

full tablespace, 7.6.3

TblSpaceFullRecovery parameter, 7.6.3

ttCacheDbCgStatus built-in procedure, 7.4 ttCacheDDLTrackingConfig built-in procedure, 7.2.7, 7.2.7 ttCachePolicySet built-in procedure, 3.6.1 ttCacheStart built-in procedure, 2.3.2, 3.6 ttCacheStop built-in procedure, 2.7.5, 3.6, 9.5 ttCacheUidGet built-in procedure, 3.5 ttCacheUidPwdSet built-in procedure, 2.1.4, 3.3.4, 10.2.3 ttDBConfig, 4.2.2.2.3 ttDbConfig built-in procedure, 8.4 ttDestroy utility, 9.6 ttGridAttach built-in procedure, 2.4, 4.7.4, 7.7

calling after database failure, 3.6.1

ttGridCreate built-in procedure, 2.2, 3.4.2.2 ttGridDestroy built-in procedure, 2.7.4, 9.4 ttGridDetach built-in procedure, 2.7.1, 9.1 ttGridDetachAll built-in procedure, 9.1 ttGridDetachList built-in procedure, 9.1 ttGridGlobalCGResume built-in procedure, 7.2.6 ttGridGlobalCGSuspend built-in procedure, 7.2.6 ttGridInfo built-in procedure, 7.2.5 TTGRIDMEMBERID() SQL function, 6.4.2 ttGridNameSet built-in procedure, 2.2, 3.4.2.3 TTGRIDNODENAME() SQL function, 6.4.2 ttGridNodeStatus built-in procedure, 7.2.5 TTGRIDUSERASSIGNEDNAME() SQL function, 6.4.2 ttIsql set dynamicloadenable command, 5.3.1 ttIsql set dynamicloaderrormode command, 5.3.4 ttIsql utility, 2.1.3, 10.2.3

cachegroups command, 2.3.3, 7.2.1

cachesqlget command

INCREMENTAL AUTOREFRESH option, 4.2.5.2

ORACLE_DDL_TRACKING option, 7.2.7

set passthrough command, 5.7.8 ttOptSetFlag built-in procedure

DynamicLoadEnable flag, 5.3.1

DynamicLoadErrorMode flag, 5.3.4

PassThrough flag, 5.7.8

ttRepAdmin -duplicate utility, 6.2.2

-keepCG option, 6.2.2

-noKeepCG option, 6.2.3

ttRepPolicySet built-in procedure, 4.2.2.1 ttRepStart built-in procedure, 2.3.4, 4.2.2.1 ttRepStateGet built-in procedure, 7.7 ttRepStateSet built-in procedure, 6.2.1 ttRepStop built-in procedure, 2.7.2, 4.2.2.1, 9.2, 9.2 ttRepSubscriberWait built-in procedure, 7.2.7, 9.3 ttStatus utility, 7.1 TypeMode connection attribute, 3.3.1

U

UID connection attribute, 3.3.1

UNIQUE HASH ON cache table attribute, 4.2.8

unload cache group

global, 5.5.1

UNLOAD CACHE GROUP statement

definition, 5.5

example, 5.5

user

create, 2.1.1

definition, 2.1.1

Oracle Database

create, 10.2.1

drop, 9.7

user managed cache group

bidirectional transmit, 4.2.4

create, 4.2.4.3, 4.2.4.3

definition, 1.2.2, 4.2.4

V

views

Oracle Database, 4.2.4, C.4.1

W

WHERE clause, 4.2.6

referencing Oracle Database PL/SQL functions, 4.2.6.2

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