Setting Up a Disk Group

Before creating file systems for a database, set up a disk group for each database. A disk group lets you group disks, volumes, file systems, and files that are relevant to a single database into a logical collection for easy administration. Because you can move a disk group and its components as a unit from one machine to another, you can move an entire database when all the configuration objects of the database are in one disk group. This capability is useful in a failover situation.

Disk Group Configuration Guidelines

Follow these guidelines when setting up disk groups for use with databases:

• Only disks that are online and do not already belong to a disk group can be used to create a new disk group.
• Create one disk group for each database.
• The disk group name must be unique. Name each disk group using the Oracle database instance name specified by the environment variable $ORACLE_SID and a dg suffix. The dg suffix helps identify the object as a disk group. Also, each disk name must be unique within the disk group.
• Never create database files using file systems or volumes that are not in the same disk group.

See Tuning for Performance for more information.