If we initiate a RESTORE database with a BACKUP controlfile defining Flash Recovery Area , RMAN execute and implicit crosscheck and catalog of entire objects within the Flash Recovery Area.
RMAN catalogs any objects within the Flash Recovery Area which can not be registered within the controlfile and if any of this files belongs to an incarnation different from CURRENT incarnation within the controlfile then changes controlfile CURRENT incarnation to the one found within the file that's being cataloged.
This avoids database from restoring backups that belong to old CURRENT incarnation.
RMAN reckon with backup available for being restored if the backup incarnation and CURRENT incarnation in controlfile are identical .
