Overview of the Components of Automatic Storage Management - Oracle 10g

The primary component of Automatic Storage Management is the disk group. You configure Automatic Storage Management by creating disk groups, which, in your database instance, can then be specified as the default location for files created in the database. Oracle provides SQL statements that create and manage disk groups, their contents, and their metadata.

A disk group consists of a grouping of disks that are managed together as a unit. These disks are referred to as ASM disks. Files written on ASM disks are ASM files, whose names are automatically generated by Automatic Storage Management. You can specify user-friendly alias names for ASM files, but you must create a hierarchical directory structure for these alias names.

You can affect how Automatic Storage Management places files on disks by specifying failure groups. Failure groups define disks that share components, such that if one fails then other disks sharing the component might also fail. An example of what you might define as a failure group would be a set of SCSI disks sharing the same SCSI controller. Failure groups are used to determine which ASM disks to use for storing redundant data. For example, if two-way mirroring is specified for a file, then redundant copies of file extents must be stored in separate failure groups.

Templates are used to provide the attribute information about ASM files created in ASM disk groups. These templates simplify file creation by mapping complex file attribute specifications into a single name. For example, a template named ONLINELOG provides the file redundancy and striping attributes for all redo log files written to ASM disks. For each disk group, Automatic Storage Management provides a set of initial system templates, as shown in the table in "Managing Disk


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