I want to mention a new feature about data guard that came with Oracle 12c. This feature is switchover verify. As you know switchover is planned role transition. So you make switchover when you want to test that whether standby database is working correctly.Before 12c you make switchover and you see an error during switchover if there is an error in dataguard configuration. But now we can check that whether data guard configuration is proper before the switchover. We can check some configuration with this verify. Some of this checked configurations are like following.
1) Whether redo apply is running on the standby
2) Whether log destination is correct
3) The version of the switchover target is 12.1 or later
This command is to use verify the instance are ready for switch over
alter database switchover to orcl_dr verify;
This command is used to switch over to DR. Now we need to run single command to switch over to DR site. Then restart the new primary instance and restart new standby as standby database.
alter database switchover to orcl_dr;