Voting disk & Oracle Cluster Registry (OCR)

Voting disk


The voting disk is a shared partition that Oracle Clusterware uses to verify cluster node membership and status. Oracle Clusterware uses the voting disk to determine which instances are members of a cluster by way of a health check and arbitrates cluster ownership among the instances in case of network failures. The primary function of the voting disk is to manage node membership and prevent what is known as Split Brain Syndrome in which two or more instances attempt to control the RAC database. This can occur in cases where there is a break in communication between nodes through the interconnect.


Oracle Clusterware supports a maximum of 32 voting disks


[oracle@racnode1 ~]$crsctl query css votedisk
0. 0 /u02/oradata/racdb/CSSFile

located 1 votedisk(s).


Add voting disk


[root@racnode1 ~]# crsctl add css votedisk /u02/oradata/racdb/CSSFile_mirror1 -force


Backup of voting disk


[root@racnode1 ~]# dd if=/u02/oradata/racdb/CSSFile of=/u03/crs_backup/votebackup/CSSFile.bak bs=4k


 Recover the voting disk 


dd if=/u03/crs_backup/votebackup/CSSFile.bak of=/u02/oradata/racdb/CSSFile bs=4k

Oracle Cluster Registry (OCR)

* Node membership information
* Database instance, node, and other mapping information
* ASM (if configured)
* Application resource profiles such as VIP addresses, services, etc.
* Service characteristics
* Information about processes that Oracle Clusterware controls
* Information about any third-party applications controlled by CRS (10g R2 and later) 


[oracle@racnode1 ~]$ ocrcheck
Status of Oracle Cluster Registry is as follows :
Version : 2
Total space (kbytes) : 262120
Used space (kbytes) : 4660
Available space (kbytes) : 257460
ID : 1331197
Device/File Name : /u02/oradata/racdb/OCRFile
Device/File integrity check succeeded
Device/File not configured
Cluster registry integrity check succeeded


Add new OCR mirror.

[root@racnode1 ~]# ocrconfig -replace ocrmirror /u02/oradata/racdb/OCRFile_mirror


Repair OCR
[root@racnode2 ~]# ocrconfig -repair ocrmirror /dev/raw/raw2


Automatic OCR Backups

The Oracle Clusterware automatically creates OCR physical backups every four hours. At any one time, Oracle always retains the last 3 backup copies of the OCR that are 4 hours old. The CRSD process that creates these 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 OCR physical backup files that Oracle retains.


[oracle@racnode1 ~]$ ocrconfig -showbackup


[root@racnode1 ~]# ocrconfig -export 




Recover OCR from Valid OCR Mirror


[root@racnode1 ~]# ocrconfig -replace ocr  /u02/oradata/racdb/OCRFile


Recover OCR from Automatically Generated Physical Backup


[root@racnode2 ~]# ocrconfig -restore /u01/app/crs/cdata/crs/backup00.ocr


Recover OCR from an OCR Export File



[root@racnode1 ~]# ocrconfig –import