In Data Guard environment your database operates in one of two Role.
1.Primary Database
2.Standby Database.
To know more about it Oracle Dataguard
You can have Physical, Logical or Snapshot database in Standby role. Primary and Standby roles are mutually exclusive.
With Data Guard role management service we can change this role dynamically and can achieve our requirement.
There are two types of Role Transition possible.
1. Switchover :
A switchover is planned role reversal. We can use this feature to change primary database role to one of an available standby database. That chosen standby database then become primary database and primary database become standby database in switchover scenario.
There is no data divergence between the original and new primary databases after successful completion of the switchover.
We don’t need to re-create any database involved in switchover task.
The switchover is very helpful for planned maintenance of hardware or operating system.
2. Failover :
We use this method when Primary Database crashes and there is no possibility to recover the primary database in a timely manner.
During a failover operation, the standby database assumes the primary database role. We need to invoke this on the standby database on which we want to failover primary role.
When we perform fail over the original primary database is presumed to be lost. If you want, you can reinstate or
re-create the original primary database as a new standby database.
It is an unplanned role transition and used in an emergency.
Depending on the data protection mode, minimum or no data loss will occur.
It can be done manually or we can configure automation for failover using FAST START FAILOVER. Fast Start Fail Over can be enabled for automatic failover. So when Primary Database is not available, Data Guard will Fail Over Primary Database role to a Configured standby database.
Stay tuned for Fast Start Fail Over Configuration.
Stay tuned for More articles on Oracle DataGuard
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