Oracle RAC Clusterware: OCR Disks

Say, you’ve just joined a new client, you are in a new RAC environment and you are trying to figure out the different components of the cluster.

Oracle Cluster Registry (OCR) is one such component in 10g RAC used to store the cluster configuration information. It is a shared disk component, typically located in a shared raw volume that must be accessible to all nodes in the cluster. The daemon OCSSd manages the configuration info in OCR and maintains the changes to cluster in the registry.

ocrcheck is the command to check out the OCR. Here is a sample output of ocrcheck.

$ocrcheck
Status of Oracle Cluster Registry is as follows :
Version : 2
Total space (kbytes) : 1048296
Used space (kbytes) : 5116
Available space (kbytes) : 1043180
ID : 834229908
Device/File Name : /dev/vx/rdsk/ocrdg/ocrvol
Device/File integrity check succeeded
Device/File Name : /dev/vx/rdsk/ocrdg/ocrvol2
Device/File integrity check succeeded

Cluster registry integrity check succeeded

The file /etc/oracle/ocr.loc can also be used for this.

$cat /etc/oracle/ocr.loc
ocrconfig_loc=/dev/vx/rdsk/ocrdg/ocrvol
ocrmirrorconfig_loc=/dev/vx/rdsk/ocrdg/ocrvol2
local_only=FALSE