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Graceful Switchover (Role Reversal)

Graceful Switchover (Role Reversal)

Jan 27, 2015

Dbvisit Standby Graceful Switchover limitations

In some cases, on Windows the registry setting ORA_DB _{}AUTOSTART needs to be set to FALSE. (where DB is the name of your database) The setting is in: HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE. (Only set this if graceful switchover is not successful initially).

If the database uses ASM, then the ASM instance must be at least Oracle version 11.1. This limitation is only for the ASM instance and not for the database itself.

How the Dbvisit Standby Graceful Switchover process works

  1. Dbvisit Standby checkpoints are used to ensure the process between the primary and standby database are synchronised.

  2. Users should be disconnected from the main primary database.

  3. Dbvisit Standby Graceful Switchover is initiated with a simple command on the primary server and the standby server.

  4. Main primary database is shutdown during transition.

  5. Standby database is shutdown during transition.

  6. Main primary database transitions to standby database on primary server in matter of minutes*.

  7. Standby database transitions to primary database on standby server in matter of minutes*.

  8. Users can re-connect to primary database on standby server and continue working, with no data loss.

  9. Maintenance can proceed on primary server.

  10. Optionally Dbvisit Standby can keep the standby database on the primary server up to date during the scheduled maintenance outage.

  11. At the end of the scheduled maintenance the databases are transitioned back to their original state in matter of minutes*.

*Depending on speed of network and distance between primary and standby server.

 

Please also see: 

 

When running Graceful Switchover in a RAC environment

Graceful Switchover (GS) is fully supported in an Oracle RAC environment.

Dbvisit Standby will be run from the primary nodes shipping logs to the standby server.  When the GS process is running, you will execute the GS command from one of the Primary RAC nodes and also on the standby server.

As with the Single Instance GS process, the same unique key must be used on both primary and standby.

It is recommended to always run a log gap report prior to running the GS process so that you can ensure that the Archive Log Gap between the primary and standby is 0 - BUT when using RAC the Archive Log gap can be 1 on one of the RAC threads (this is as you will not always be able to get a 0 archive log gap for all threads.

Perform Graceful Switchover using either GUI or CLI.  If using the GUI - from the Run Interactive Screen select the Database (DDC) and then the Graceful Switchover option in drop down, provide a Unique key and click on next.  If using the CLI - run the command: ./dbv_oraStartStop switchover DDC <unique_key>

Note: you still have to run the switchover step on both the primary node (only one of them) and the standby node using the same unique key.

 

At the end of the Graceful Switchover where the Oracle RAC environment become the primary again, there will be a message showing you that you can enable the RAC database (all nodes by doing following).

This final step needs to be executed by the Database Administrator as the reason for the GS might have been to add RAC nodes or remove nodes etc.  


1.  Update the cluster_database=true in spfile
2.  Update the cluster_database_instances=X in the spfile - where X is the number of instances you have configured for this RAC database.
3.  Shutdown the instance, then start the Cluster database using the "srvctl" command - srvctl start database -d DB_UNIQUE_NAME