Identify the scenarios in which the RMAN CROSSCHECK comm and is useful. (Choose all that apply.)
A.To check that the obsolete backups are deleted from the repository records and from the disk.
B.To update the RMAN repository if you delete archived redo logs with operating system commands.
C.To update outdated information about backups that disappeared from disk or tape or became corrupted and inaccessible.
D.To synchronize the actual files on disk or in the media management catalog with the RMAN repository for which the backup was not taken using RMAN.
Crosschecks are useful because they can do the following:
Update outdated information about backups that disappeared from disk or tape or became corrupted
Update the repository if you delete archived redo logs or other files with operating system commands
原文：http://www.cnblogs.com/Babylon/p/7837997.html