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-> OCR file & Voting disk in an Oracle RAC Clusterware

 

 OCR file & Voting disk in an Oracle RAC Clusterware

 

 

Oracle Clusterware includes the following processes:

 

1) Oracle Cluster Registry (OCR)

       

     - this is the central repository for the Oracle cluster: there we find all the information about the cluster in real-time;

     - CRS update the OCR with the information about the node failure or reconfiguration;

     - CSS update the OCR when a node is added or deleted;

     - NetCA, DBCA, SRVCTL update the OCR with the services information;

     - this is a binary file and cannot be edited;

     - the OCR information is cached on each node;

     - only one node (the master node) can update the OCR file => The master node has the OCR cache up-to-date in real time;

     - OCR file is automatically backed up in the OCR location every 4 hours:

 

           cd $CRS_HOME/cdata/<cluster name>

         ls
         backup00.ocr backup01.ocr backup02.ocr day.ocr day_.ocr week.ocr

 


     - OCR file can be backud up manually as well running the following command:

                  dd if=voting_disk_name of=backup_file_name

 

     - the OCR files are backed up for a week and overwritten in a circulary manner;

     - because the OCR is a key component of the Oracle cluster, the OCR file must be mirrored;

     - the OCR file can be exported, imported with ocrconfig command;    


 


2) Oracle Voting Disk

     - all the nodes ping the voting disk;

     - if the cluster see that a node cannot ping the voting disk, the cluster consider that node that is no longer a valid node and evicts the node from the cluster;

     - this file is very important for the cluster and must be mirrored.

    

 

!!!  One file system must have 560 MB of available space for the primary OCR and a voting disk.   !!!

 

 

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