Why would you execute the report obsolete command?
A.
To list all backups that were no longer available for restore operations
B.
To list all backups that had aged beyond the RMAN retention criteria
C.
To list all backup set pieces listed in control-file or recovery-catalog metadata that are not
on the backup media
D.
To list all datafiles that are no longer part of the database and thus do not need to be
backed up
E.
To list all archived redo logs that are no longer needed for any database recovery
Explanation:
You can report backup sets, backup pieces, and data file copies that are obsolete that is, not
needed to meet a specified retention policy by specifying the OBSOLETE keyword.
B is correct:
https://docs.oracle.com/cd/B28359_01/backup.111/b28270/rcmreprt.htm
Reporting on Obsolete Backups
You can report backup sets, backup pieces and datafile copies that are obsolete, that is, not needed to meet a specified retention policy, by specifying the OBSOLETE keyword.
To report obsolete backups:
Start RMAN and connect to a target database and recovery catalog (if used).
Execute the CROSSCHECK command to update the status of backups in the repository compared to their status on disk.
In the simplest case, you could crosscheck all backups on disk, tape or both, using any one of the following commands:
CROSSCHECK BACKUP DEVICE TYPE DISK;
CROSSCHECK BACKUP DEVICE TYPE sbt;
CROSSCHECK BACKUP; # crosshecks all backups on all devices
See Chapter 11, “Maintaining RMAN Backups and Repository Records” for more details on how to update the RMAN repository record to contain the actual set of available backups.
Run REPORT OBSOLETE to identify which backups are obsolete because they are no longer needed for recovery.
If you do not specify any other options, then REPORT OBSOLETE displays the backups that are obsolete according to the current retention policy, as shown in the following example:
RMAN> REPORT OBSOLETE;