Oracle Solution for Error ora-38857

ORA-38857: cannot mark redo thread string as enabled

What triggered the Error:

The standby switchover or failover operation failed because it needs to mark a redo thread as enabled. However, the control file was recreated with a MAXINSTANCES value smaller than the thread number of the redo thread.

What should we do to fix it:

Recreate the control file with a larger MAXINSTANCES value.