The Oracle Cluster Registry (OCR) contains cluster and database configuration and state information for Oracle RAC and Oracle Clusterware/Grid Infrastructure.
The information maintained in the OCR includes:
The list of nodes
The mapping of database instances to nodes
Oracle Clusterware application resource profiles
Resource profiles that define the properties of resources under Oracle Clusterware/Grid Infrastructure control
Rules that define dependencies between the Oracle Clusterware/Grid Infrastructure resources
The current state of the cluster
For versions prior to Oracle RAC 11g Release 2, the OCR data exists on a shared raw volume or a cluster file system that is accessible to each node.
In Oracle RAC 11g Release 2 and later versions, the OCR data exists on ASM or a cluster file system that is accessible to each node.
Use CVM mirrored volumes to protect OCR data from failures.Oracle Clusterware/Grid Infrastructure faults nodes if OCR is not accessible because of corruption or disk failure. Oracle automatically backs up OCR data. You can also export the OCR contents before making configuration changes in Oracle Clusterware/Grid Infrastructure. This way, if you encounter configuration problems and are unable to restart Oracle Clusterware/Grid Infrastructure, you can restore the original contents.
Consult the Oracle documentation for instructions on exporting and restoring OCR contents.