Exam 1z0-062 topic 1 question 272 discussion

"To ensure that data about backups in the recovery catalog or control file is synchronized with corresponding data on disk or in the media management catalog, perform a crosscheck. " "Crosschecks update outdated RMAN repository information about backups whose repository records do not match their physical status. For example, if a user removes archived logs from disk with an operating system command, the repository still indicates that the logs are on disk, when in fact they are not." Option D is right apart from the fact that RMAN does not check for validity of Tape backups, so corruption in Tape backups are not picked by RMAN. https://docs.oracle.com/database/121/ADMQS/GUID-F9FC18D6-6FCA-4C6D-9B34-250470469495.htm#ADMQS0953

Noted: Use the CROSSCHECK command to synchronize the "physical reality of backups" and copies with their logical records in the RMAN repository. But B ,is to synchronize the logical with physical. B is not correct

Per Oracle Documentation for 12.1 A: "CROSSCHECK validates all specified backups and copies, even if they were created in previous database incarnations." B: "synchronize the physical reality of backups and copies with their logical records in the RMAN repository." D: "If a backup is on disk, then CROSSCHECK determines whether the header of the file is valid. If a backup is on tape, then RMAN queries the RMAN repository for the names and locations of the backup pieces to be checked. RMAN sends this metadata to the target database server, which queries the media management software about the backups. The media management software then checks its media catalog and reports back to the server with the status of the backups."

Purpose Use the CROSSCHECK command to synchronize the physical reality of backups and copies with their logical records in the RMAN repository.

I think A,B,D https://docs.oracle.com/database/121/RCMRF/rcmsynta014.htm#RCMRF119