It is sometimes necessary to relocate backups to another directory for operational reasons e.g. space management or file system mount points.
The CATALOG command allows one or more backup files to be registered with the catalog within the control file and optionally in the RMAN catalog database.
To register all backup files within a directory use
CATALOG START WITH
For example:
CATALOG START WITH '/u01/oracle/backup/TEST';
The above command will register all backup files in the /u01/oracle/backup/TEST directory with the RMAN catalogs.