About Creating an Oracle Database

After you plan your database using some of the guidelines presented in this section, you can create the database with a graphical tool or a SQL command. You typically create a database during Oracle Database software installation. However, you can also create a database after installation. Reasons to create a database after installation are as follows:

You used Oracle Universal Installer (OUI) to install software only, and did not create a database.
You want to create another database (and database instance) on the same host computer as an existing Oracle database. In this case, this chapter assumes that the new database uses the same Oracle home as the existing database. You can also create the database in a new Oracle home by running OUI again.
You want to make a copy of (clone) a database.

The specific methods for creating a database are:

With Database Configuration Assistant (DBCA), a graphical tool.

See "Creating a Database with DBCA"
With the CREATE DATABASE SQL statement.

See "Creating a Database with the CREATE DATABASE Statement"

Considerations Before Creating the Database

Database creation prepares several operating system files to work together as an Oracle Database. You need only create a database once, regardless of how many datafiles it has or how many instances access it. You can create a database to erase information in an existing database and create a new database with the same name and physical structure.

The following topics can help prepare you for database creation.

Planning for Database Creation
Meeting Creation Prerequisites

Planning for Database Creation

Prepare to create the database by research and careful planning. Table 2-1 lists some recommended actions:

Table 2-1 Database Planning Tasks

Action	Additional Information
Plan the database tables and indexes and estimate the amount of space they will require.	Part II, "Oracle Database Structure and Storage" Part III, "Schema Objects"
Plan the layout of the underlying operating system files your database will comprise. Proper distribution of files can improve database performance dramatically by distributing the I/O during file access. You can distribute I/O in several ways when you install Oracle software and create your database. For example, you can place redo log files on separate disks or use striping. You can situate datafiles to reduce contention. And you can control data density (number of rows to a data block). If you create a Flash Recovery Area, Oracle recommends that you place it on a storage device that is different from that of the datafiles.	Oracle Database Performance Tuning Guide Oracle Database Backup and Recovery User's Guide Your Oracle operating system–specific documentation, including the appropriate Oracle Database installation guide.
Consider using Oracle-managed files and Automatic Storage Management to create and manage the operating system files that make up your database storage.	Chapter 15, "Using Oracle-Managed Files" Oracle Database Storage Administrator's Guide
Select the global database name, which is the name and location of the database within the network structure. Create the global database name by setting both the `DB_NAME` and `DB_DOMAIN` initialization parameters.	"Determining the Global Database Name"
Familiarize yourself with the initialization parameters contained in the initialization parameter file. Become familiar with the concept and operation of a server parameter file. A server parameter file lets you store and manage your initialization parameters persistently in a server-side disk file.	"About Initialization Parameters and Initialization Parameter Files" "What Is a Server Parameter File?" Oracle Database Reference
Select the database character set. All character data, including data in the data dictionary, is stored in the database character set. You must specify the database character set when you create the database. If clients using different character sets will access the database, then choose a superset that includes all client character sets. Otherwise, character conversions may be necessary at the cost of increased overhead and potential data loss. You can also specify an alternate character set. Caution: `AL32UTF8` is the Oracle Database character set that is appropriate for XMLType data. It is equivalent to the IANA registered standard `UTF-8` encoding, which supports all valid XML characters. Do not confuse Oracle Database database character set `UTF8` (no hyphen) with database character set `AL32UTF8` or with character encoding `UTF-8`. Database character set `UTF8` has been superseded by `AL32UTF8`. Do not use `UTF8` for XML data. `UTF8` supports only Unicode version 3.1 and earlier; it does not support all valid XML characters. `AL32UTF8` has no such limitation. Using database character set `UTF8` for XML data could potentially cause a fatal error or affect security negatively. If a character that is not supported by the database character set appears in an input-document element name, a replacement character (usually "?") is substituted for it. This will terminate parsing and raise an exception.	Oracle Database Globalization Support Guide
Consider what time zones your database must support. Oracle Database uses one of two time zone files as the source of valid time zones. The default time zone file is `timezonelrg.dat`. It contains more time zones than the other time zone file, `timezone.dat`.	"Specifying the Database Time Zone File"
Select the standard database block size. This is specified at database creation by the `DB_BLOCK_SIZE` initialization parameter and cannot be changed after the database is created. The `SYSTEM` tablespace and most other tablespaces use the standard block size. Additionally, you can specify up to four nonstandard block sizes when creating tablespaces.	"Specifying Database Block Sizes"
Determine the appropriate initial sizing for the `SYSAUX` tablespace.	"About the SYSAUX Tablespace"
Plan to use a default tablespace for non-`SYSTEM` users to prevent inadvertent saving of database objects in the `SYSTEM` tablespace.	"Creating a Default Permanent Tablespace"
Plan to use an undo tablespace to manage your undo data.	Chapter 14, "Managing Undo"
Develop a backup and recovery strategy to protect the database from failure. It is important to protect the control file by multiplexing, to choose the appropriate backup mode, and to manage the online and archived redo logs.	Chapter 10, "Managing the Redo Log" Chapter 11, "Managing Archived Redo Logs" Chapter 9, "Managing Control Files" Oracle Database Backup and Recovery User's Guide
Familiarize yourself with the principles and options of starting up and shutting down an instance and mounting and opening a database.	Chapter 3, "Starting Up and Shutting Down"

Meeting Creation Prerequisites

Before you can create a new database, the following prerequisites must be met:

The desired Oracle software must be installed. This includes setting various environment variables unique to your operating system and establishing the directory structure for software and database files.
Sufficient memory must be available to start the Oracle Database instance.
Sufficient disk storage space must be available for the planned database on the computer that runs Oracle Database.

All of these are discussed in the Oracle Database Installation Guide specific to your operating system. If you use the Oracle Universal Installer, it will guide you through your installation and provide help in setting environment variables and establishing directory structure and authorizations.