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Oracle® Database 2 Day DBA
11g Release 1 (11.1)

Part Number B28301-03
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About Automatic Storage Management

Automatic Storage Management (ASM) is an integrated, high-performance database file system and disk manager. You use ASM instead of an operating system file system to store your database files.

ASM is based on the principle that the database should manage storage instead of requiring an administrator to do it. ASM eliminates the need for you to manage potentially thousands of database files.

ASM groups the disks in your storage system into one or more disk groups. You manage a small set of disk groups, and ASM automates the placement of the database files within those disk groups.

ASM provides the following benefits:

Oracle recommends that you use ASM for your database file storage, instead of raw devices or the operating system file system. However, databases can have a mixture of ASM files and non-ASM files. Oracle Enterprise Manager includes a wizard that enables you to migrate non-ASM database files to ASM.

The ASM Instance

ASM is implemented as a special kind of Oracle instance, with its own System Global Area and background processes. The ASM instance is tightly integrated with the database instance. Every server running one or more database instances that use ASM for storage has an ASM instance. In an Oracle Real Application Clusters environment, there is one ASM instance for each node, and the ASM instances communicate with each other on a peer-to-peer basis. Only one ASM instance is required for each node, regardless of the number of database instances on the node.

Administering ASM

You administer ASM with Oracle Enterprise Manager Database Control (Database Control). To administer the ASM instance and ASM disk groups, you must connect to the ASM instance as a user who has been granted the SYSASM system privilege. When you create the ASM instance with Oracle Database Configuration Assistant (DBCA), DBCA grants SYSASM to user SYS.