Storing Oracle Cluster Registry and Voting Files in Oracle ASM Disk Groups

You can store Oracle Cluster Registry (OCR) and voting files in Oracle ASM disk groups. You can also store a backup of the OCR file in a disk group. Voting files and OCR are two important components of Oracle Clusterware. Voting files manage information about node membership. OCR manages cluster and Oracle Real Application Clusters (Oracle RAC) database configuration information.

A quorum failure group is a special type of failure group that does not contain user data. Quorum failure groups are used for storing Oracle ASM metadata. A quorum failure group may also contain voting files if those files are stored in a disk group that contains a quorum failure group. Additionally, Oracle ASM uses a quorum failure group to help determine if the disk group can be mounted in the event of the loss of one or more failure groups.

Because disks in quorum failure groups do not contain user data, a quorum failure group is not considered when determining redundancy requirements in respect to storing user data. For information about failure groups, see "Oracle ASM Failure Groups".

You can manage and monitor OCR and voting files with CRSCTL and ocrconfig command-line tools, CREATE and ALTER DISKGROUP SQL statements, and V$ASM views.

The CRSCTL and ocrconfig commands enable the placement of OCR storage and Cluster Synchronization Services (CSS) voting files inside the disk groups managed by Oracle ASM.

The QUORUM and REGULAR keywords in CREATE and ALTER DISKGROUP SQL statements enable the specification of an additional qualifier for failure groups or disks when creating or altering a disk group. Note that QUORUM disks (or disks in QUORUM failure groups) cannot contain user data, while REGULAR disks (or disks in non-quorum failure groups) do not have this restriction.

You can use these keywords before the keyword FAILGROUP if a failure group is being explicitly specified. If the failure group is implicitly implied, you can use these keywords (QUORUM/REGULAR) before the keyword DISK. When failure groups are explicitly specified, it is an error to specify these keywords (QUORUM/REGULAR) immediately before the keyword DISK. REGULAR is the default failure group type.

When performing operations on existing disks or failure groups, the qualifier specified in the SQL must match the qualifier that was specified when the disks or failure groups were added to the disk group.

Example 4-4 shows the creation of a disk group with a QUORUM failure group. For Oracle Clusterware files a minimum of three disk devices or three failure groups is required with a normal redundancy disk group. A QUORUM failure group is not considered when determining redundancy requirements in respect to storing user data. The COMPATIBLE.ASM disk group compatibility attribute must be set to 11.2 or greater to store OCR or voting files in a disk group.

The FAILGROUP_TYPE column in the V$ASM_DISK or V$ASM_DISK_STAT views specifies the failure group type. The value for this column is REGULAR for regular failure groups and QUORUM for quorum failure groups.

The VOTING_FILE column in the V$ASM_DISK or V$ASM_DISK_STAT views specifies whether a disk contains a voting file. The value for this column is either Y if the disk contains a voting file or N if not.

The value of USABLE_FILE_MB in V$ASM_DISKGROUP or V$ASM_DISKGROUP_STAT does not consider any free space that is present in QUORUM disks because that space is not available for client data files.

For information about V$ASM views, refer to "Views Containing Oracle ASM Disk Group Information".

CREATE DISKGROUP ocr_data NORMAL REDUNDANCY
   FAILGROUP fg1 DISK '/devices/diskg1'
   FAILGROUP fg2 DISK '/devices/diskg2'
   QUORUM FAILGROUP fg3 DISK '/devices/diskg3'
   ATTRIBUTE 'compatible.asm' = '12.1.0.0.0';