"media recovery required"
*Cause: An error has occurred while performing a switchover.
*Action: If you were switching a primary database to the standby role, the
conversion was successful, but one or more errors occurred after
the conversion completed. See the alert log for more information.
You can proceed with switching the target standby database to the
primary role, but you must address the errors reported at the old
primary database before it can protect the new primary database.
If you encountered this error while switching a physical standby
database to the primary role, the switchover did not succeed
because additional redo must be applied. Verify that redo apply is
active and wait until the SWITCHOVER_STATUS column of the
V$DATABASE dynamic performance view reports TO_PRIMARY or
SESSIONS_ACTIVE before retrying the switchover.