RAC

OCR is a file that manages cluster and Oracle Real Application Clusters (Oracle RAC) database configuration information. The OCR contains information about the cluster node list, instance-to-node mapping information, and information about Oracle Clusterware resource profiles for applications

This is a Very important component along with Voting Disk and Loss of it will require you to re-install the Clusterware Software.

Oracle 10g provides Automatic Backup of OCR along with manually export of OCR files.

Starting from Oracle 11g, we can also take manual backups of OCR. So in 11g , we can have following backups

1) Automatic backups—Oracle Clusterware automatically creates OCR backups every four hours. At any one time, Oracle always retains the last three backup copies of the OCR. The CRSD process that creates the backups 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 retains.

We can view the backups using ocrconfig -showbackup auto command.

[oracle@prod01]/home/oracle>ocrconfig -showbackup auto
prod01     2008/05/14 19:23:22     /u01/app/11.1.0/crs/cdata/prod_cluster/backup00.ocr
prod01     2008/05/14 15:23:21     /u01/app/11.1.0/crs/cdata/prod_cluster/backup01.ocr
prod01     2008/05/14 11:23:21     /u01/app/11.1.0/crs/cdata/prod_cluster/backup02.ocr
prod01     2008/05/13 15:23:20     /u01/app/11.1.0/crs/cdata/prod_cluster/day.ocr
prod01     2008/05/04 01:52:33     /u01/app/11.1.0/crs/cdata/prod_cluster/week.ocr

2)Manual backups—You can use the ocrconfig -manualbackup command to force Oracle Clusterware to perform a backup of the OCR at any time, rather than wait for the automatic backup that occurs at 4-hour intervals. The -manualbackup option is especially useful when you to need to obtain a binary backup on demand, such as before you make changes to the OCR.

You need to be logged in as root user to take manual backups. Use ocrconfig –manualbackup command. To view the backups use ocrconfig –showbackup manual command

[oracle@prod01]/home/oracle>ocrconfig -showbackup manual
prod01     2008/05/01 12:21:29     /u01/app/11.1.0/crs/cdata/prod_cluster/backup_20080501_122129.ocr
prod02     2008/04/11 11:32:50     /u01/app/11.1.0/crs/cdata/prod_cluster/backup_20080411_113250.ocr
prod02     2008/03/27 17:25:23     /u01/app/11.1.0/crs/cdata/prod_cluster/backup_20080327_172523.ocr

3)Manual Export—You can Use the ocrconfig -export file_name command to export the OCR content to a file format.

For more details refer to 11g Documentation