2.2.9 Enabling the Oracle ASM appliance.mode Attribute

The Oracle ASM appliance.mode attribute improves disk rebalance completion time when dropping one or more Oracle ASM disks.

Setting the appliance.mode attribute helps restore redundancy faster after a failure. The attribute can only be enabled on disk groups that meet the following requirements:

• The Oracle ASM disk group attribute compatible.asm is set to release 11.2.0.4, or 12.1.0.2 or later.

• The cell.smart_scan_capable attribute is set to TRUE.

• All disks in the disk group are the same type; for example, all disks are hard disks or all disks are flash disks.

• All disks in the disk group are the same size.

• All failure groups in the disk group have an equal number of disks:

  • For eighth rack configurations, all failure groups have 4 disks, or all failure groups have 6 disks.

  • For all other rack configurations, all failure groups have 10 disks, or all failure groups have 12 disks.

• There are at least 3 failure groups in the disk group.

• No disk in the disk group is offline.

Note:

Enabling the appliance.mode attribute for existing disk groups may cause an increase of data movement during the next rebalance operation.

The appliance.mode attribute is automatically enabled when creating a new disk group. Existing disk groups must explicitly set the attribute using the ALTER DISKGROUP command.

SQL> ALTER DISKGROUP disk_group SET ATTRIBUTE 'appliance.mode'='TRUE';

Note:

The appliance.mode attribute should normally be set to TRUE. In rare cases it may be necessary to disable appliance.mode as a workaround when adding disks to a disk group. After the disk group is ALTERed enable appliance.mode, and perform a REBALANCE operation.

To disable the appliance.mode attribute during disk group creation, set the attribute to FALSE.

SQL> CREATE DISKGROUP data NORMAL REDUNDANCY
DISK
'o/*/DATA*'
ATTRIBUTE 'content.type' = 'data',
          'au_size' = '4M',
          'cell.smart_scan_capable'='TRUE',
          'compatible.rdbms'='11.2.0.3',
          'compatible.asm'='11.2.0.4',
          'appliance.mode'='FALSE';