Explanation/Reference:
Explanation:

Use the CATALOG command to do the following:
Add backup pieces and image copies on disk to the RMAN repository
Record a data file copy as a level 0 incremental backup in the RMAN repository, which enables you to use it as part of an incremental backup strategy START WITH 'string_pattern' Catalogs all valid backup sets, data file and control file copies, and archived redo log files whose name start with string_pattern. The string pattern can be an ASM disk group, Oracle-managed files directory, or part of a file name (see Example 2-32).
RMAN reports any files in the disk location that it cannot catalog. RMAN must be connected to a mounted target database.
If the string pattern specifies a file name, then it matches the left part of the file name pattern. For example,
/tmp/arc matches everything in directory /tmp/arc_dest and /tmp/archive/january as well as file /tmp/ arc.cpy. Note: You cannot use wildcard characters in the string pattern, only a strict prefix.