Recovery Manager Restore and Recovery Techniques - Oracle 10g/11g Data and Database Management Utilities - page 150

Crosscheck command
The crosscheck command is used to validate the physical backup is located where
rman thinks it is. rman stores the backup information either in the controlfile or
in the rman repository. If a restore operation needs to be carried out, rman determines
the best suitable backupset and archivelog files required to successfully perform
the recover process. If the backup is not where it is supposed to be then there will
be problems.
In the following scenario rman validates the backup sets:
There are three backupsets, this can be queried using the LIST BACKUP command ( A ):
LIST BACKUP OF TABLESPACE USERS SUMMARY;