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Dbvisit automatic Graceful switchover

Graceful switchover (also referred to as role reversal or seamless switchover) can be used to switch back to original configuration as it was before the disaster. This is a seamless operation done in a matter of minutes with no dataloss.

Graceful switchover is also be used for planned outages (or scheduled maintenance) to perform an upgrade on the primary site while keeping the system available for all users. This is done by reversing the roles between the primary and standby database and switching the database users over to the standby site during the outage. It may also be used to test the Disaster Recovery (DR) scenario.

During a switchover, the primary database transitions to a standby role, and the standby database transitions to a primary role. There is no data loss during the transition and the standby database does not have to be rebuilt. Dbvisit Graceful switchover has been tested with Oracle 8i, 9i, 10g and 11g.

How the Dbvisit Graceful switchover process works after a disaster to switch back to the original (pre-disaster) configuration:

1. The standby database has been activated to become the new primary database during the disaster.
2. Users are using the new primary database on standby server which has become the main database.
3. Standby database is rebuild on the original primary server (Users are not affected).
4. Dbvisit Graceful switchover is initiated with a simple command on both servers.
5. Users are temporarily disconnected from the primary database on the standby server.
6. Primary database on standby server is temporarily shutdown during transition.
7. Standby database on the original primary server is temporarily shutdown during transition.
8. Standby database transitions to primary database on the original primary server in matter of minutes* in a seamless operation.
9. Primary database transitions to standby database on standby server in matter of minutes* in a seamless operation.
10. Users can re-connect after a few minutes to new primary database on the original primary server and continue working, with no data loss.
11. Original configuration is restored (pre-disaster) in matter of minutes* with simple command!
12. Dbvisit automatically keeps the original standby database on the standby server up to date. No configurational change required!

How the Dbvisit Graceful switchover process works for planned outages:

1. Dbvisit Graceful switchover is initiated with a simple command on both servers.
2. Users are temporarily disconnected from the main primary database.
3. Main primary database is temporarily shutdown during transition.
4. Standby database is temporarily shutdown during transition.
5. Main primary database transitions to standby database on primary server in matter of minutes* in a seamless operation.
6. Standby database transitions to primary database on standby server in matter of minutes* in a seamless operation.
7. Users can re-connect to new primary database on standby server and continue working, with no data loss.
8. Maintenance can proceed on primary server.
9. Optionally Dbvisit can keep the standby database on the primary server up to date during the scheduled maintenance outage.
10. At the end of the scheduled maintenance the databases are transitioned back to their original state in matter of minutes*.

Difference between Graceful switchover and Failover:
Graceful switchover is not used during a disaster where the primary database is no longer available. The process that occurs during a disaster is called failover. During the failover the standby database is activated to become the primary database.
Activating the standby database so that it can take over instantly is done through a simple Dbvisit command:
dbv_oraStartStop activate database

Graceful switchover cannot be used together with Oracle RAC or where the redo logs or the archive logs are in Oracle ASM file system.
Note: This does not apply to Failover. Failover works with Oracle RAC and ASM.

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

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