1. Create default tablespace to rman utility user (OPTIONAL)

sqlplus / as sysdba

SQL*Plus: Release 11.2.0.2.0 Production on Wed Oct 24 02:51:36 2012

Copyright (c) 1982, 2010, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 – 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL>create tablespace varun datafile ‘/o001/app/oracle/PSDMO7/varun.dbf’ size 250m;

Tablespace created.

2.creating RMAN utility user in database to store backup info.

SQL> create user varun identified by varun default tablespace varun quota unlimited on varun;

User created.

SQL> grant recovery_catalog_owner to varun;

Grant succeeded.
SQL> exit

3. Creating CATALOG database

$ rman catalog varun/varun

Recovery Manager: Release 11.2.0.2.0 – Production on Wed Oct 24 03:25:46 2012

Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.

connected to recovery catalog database

RMAN> create catalog;

recovery catalog created

RMAN>

4. Registering Target Database under catalog database

$rman target kumar/kumar@PSDMO8 catalog varun/varun

Recovery Manager: Release 11.2.0.2.0 – Production on Wed Oct 24 03:36:18 2012

Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.

connected to target database: PSDMO8 (DBID=3631729544)
connected to recovery catalog database

RMAN> register database;

database registered in recovery catalog
starting full resync of recovery catalog
full resync complete

RMAN>

NOTE:If you see any issues related to privileges while registering database, you can grant sysdba privilege to rman utility user on target database  ” grant sysdba to varun” after creating catalog database. Granting sysdba to rman utility user is not recommended.