RMAN-20001: target database not found in recovery catalog

You may encounter this error when you try to connect with to a dataabse with RMAN Catalog

RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of set command at 09/26/2011 14:03:09
RMAN-06004: ORACLE error from recovery catalog database: RMAN-20001: target database not found in recovery catalog


This error means that your database is not registered in the RMAN catalog and you need to register it first before starting backups.

Solution:

1- Connect with the database to the RMAN catalog
$ rman catalog rman/rman@catalog target rmanbkp/rmanbkp123@orcl

2- Unregister the database
RMAN> unregister database noprompt;

3- Register Database to RMAN catalog
RMAN> register database;

4- Resync RMAN catalog
RMAN> resync catalog;