Oracle Database Tips by Donald Burleson

Oracle10g Grid Computing with RAC
Chapter 8 - RAC Administration

The Oracle Cluster Registry (OCR) in Real Application Clusters

The purpose of the OCR is to hold cluster and database configuration information for RAC and Cluster Ready Services (CRS) such as the cluster node list, and cluster database instance to node mapping, and CRS application resource profiles.

There are two methods of copying OCR content and using the content for recovery. The first method uses automatically generated physical OCR file copies and the second method uses manually created logical OCR export files.

Management of the Oracle Cluster Registry Backup Files in Real Application Clusters

The CRS are managed by a CRS instance, there will be one CRS instance for each node in a RAC cluster. In a cluster one nodes CRS instance automatically creates an OCR backup every four hours. At any one time, the last three backup copies are automatically retained. The CRS instance also creates and retains an OCR backup for each full day and at the end of each week. You cannot customize the backup frequencies or the number of files that Oracle will retain, they are completely controlled by the CRS instance.