How to unregister the database from catalog

Steps - 

1)

SQL> conn rman@RMANCAT (CATALOG SERVER DATABASE) 

Enter password:

Connected.

2)

SQL> select NAME,DBID,DB_KEY from rc_database where name='ABC';

NAME           DBID     DB_KEY

-------- ---------- ----------

ABC      2311686309    5021072

3)

SQL> EXECUTE rman.dbms_rcvcat.unregisterdatabase(5021072,2311686309);

PL/SQL procedure successfully completed.

4)

SQL> select NAME,DBID,DB_KEY from rc_database where name='ABC';

no rows selected