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Usually switchover comes in handy for maintenance activities. It’s also need a standard operating procedure to do the switchover of a critical database.

 

Pre-requisites before switch over: (assuming databases are configures for switchover)

— No lag.
— No active sessions.
— Shutdown other instances in both primary and standby.
— Service role changes before switchover (RAC)

Select * from v$dataguard_stats; — on standby to find the lag
Select name, switchover_status, database_role from v$database; — On primary

switchover_status mush to TO STANDBY, that means DB is ready for switchover.

On Primary:
— alter system switch logfile; or alter system archive log current; (in RAC).
— Shutdown the all other instances except one.
— alter database commit to switchover to pysical standby with session shutdown;
— shutdown and startup nomount;
— alter database mount standby database;

Now Come to standby db>

On Standby:

— Bring down other instances except one.
— alter database commit to switchover to primary with session shutdown;
— shutdown
— startup  — This will bring up in normal mode.
— start the services
— This is the new primary database.

Now come to old primary:

— alter database recover managed standby database disconnect session;

 

** Do pre and post checks of services, and status on both primary and standby environments.