ORA-16459：recovery already beyond standby failover

解决方法：Determine the STANDBY_BECAME_PRIMARY_SCN by selecting it from V$DATABASE on the new primary database. Then, flashback the target database to this SCN and use RMAN to delete all archive logs at or beyond this SCN. Finally, fetch all terminal end-of-redo (EOR) logs corresponding to the failover operation from the new primary database and register all these logs at the target database. Restart Redo Apply.