文档解释
ORA-16139: 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.
