Creating Disk Groups for Data and Fast Recovery Area

This topic discusses how to create a disk group for data and a disk group for the fast recovery area.

The SQL statement in Example 4-1 creates a disk group named data with normal redundancy consisting of two failure groups controller1 or controller2 with four disks in each failure group. The data disk group is typically used to store database data files.

The example assumes that the ASM_DISKSTRING initialization parameter is set to the '/devices/*' string. Oracle ASM disk discovery identifies diska1 through diska4 and diskb1 through diskb4 in the /devices directory.

In Example 4-1, the NAME clauses enable you to explicitly assign names to the disks rather than the default system-generated names. The system-generated names are in the form diskgroup_nnnn, where nnnn is the disk number for the disk in the disk group. For information about the disk name format when using Oracle ASM Filter Driver, refer to "Oracle ASM Filter Driver".

When creating the disk group in Example 4-1, the values of following disk group attributes were explicitly set:


    Specifies the size of the allocation unit for the disk group. For information about allocation units, see "About Oracle ASM Allocation Units ".

    You can view the value of the AU_SIZE disk group attribute in the ALLOCATION_UNIT_SIZE column of the V$ASM_DISKGROUP view.


    Determines the minimum software version for any Oracle ASM instance that uses a disk group. For information about the COMPATIBLE.ASM attribute, see "COMPATIBLE.ASM".


    Determines the minimum software version for any database instance that uses a disk group. For information about the COMPATIBLE.RDBMS attribute, see "COMPATIBLE.RDBMS".


    Determines whether the disk group can contain Oracle ADVM volumes. For information about the COMPATIBLE.ADVM attribute, see "COMPATIBLE.ADVM".

In Example 4-2, the fra disk group (typically created for the fast recovery area) is created with the default disk group attribute values. Names are not specified for the Oracle ASM disks and failure groups are not explicitly specified. This example assumes that diskc1 through diskc9 are present in the /devices directory.

Example 4-1 Creating the DATA disk group

  FAILGROUP controller1 DISK
    '/devices/diska1' NAME diska1,
    '/devices/diska2' NAME diska2,
    '/devices/diska3' NAME diska3,
    '/devices/diska4' NAME diska4
  FAILGROUP controller2 DISK
    '/devices/diskb1' NAME diskb1,
    '/devices/diskb2' NAME diskb2,
    '/devices/diskb3' NAME diskb3,
    '/devices/diskb4' NAME diskb4
  ATTRIBUTE 'au_size'='4M',
    'compatible.asm' = '11.2', 
    'compatible.rdbms' = '11.2',
    'compatible.advm' = '11.2';

Example 4-2 Creating the FRA disk group

  DISK '/devices/diskc*';