Recovery Catalog

Creating Recovery catalog:
Catalog database is :UAT
Target database is :DEV
Enter the Tns entries in DEV and UAT.
Tns entries in DEV
$cd $TNS_ADMIN
edit tnsname.ora
Here enter the tns entries of UAT instance
[oradev@sreenidba DEV_sreenidba]$vi tnsnames.ora
UAT=
        (DESCRIPTION=
                (ADDRESS=(PROTOCOL=tcp)(HOST=sreeni.dba.sreenidba.com)(PORT=1532))
            (CONNECT_DATA=
                (SERVICE_NAME=UAT)
                (INSTANCE_NAME=UAT)
            )
        )
TNS Entries in UAT:
here enter the tns entries DEV instance
[orauat@sreenidba UAT_sreenidba]$vi tnsnames.ora
DEV=
        (DESCRIPTION=
                (ADDRESS=(PROTOCOL=tcp)(HOST=sreenidba..sreenidba.com)(PORT=1529))
            (CONNECT_DATA=
                (SERVICE_NAME=DEV)
                (INSTANCE_NAME=DEV)
            )
        )
creating catalog user and tablespace in UAT
SQL>create tablespace ract_tab datafile'/d01/oradata/UAT/ract_tab01.dbf' size 2g;

tablespace created.
SQL>create user rcat identified by rcat default tablecpace rcat_tab quota unlimited on rcat_tab;

User created.

Grant RECOVERY_CATALOG_OWNER role to recovery catlog user

SQL> grant recovery_catalog_owner to rcat;

Grant succeeded.

Connect to target DB (DEV) and recovery catlog DB (UAT) to create catalog:
[oradev@sreenidba DEV_sreenidba]$ rman target / catalog rcat/rcat@UAT

Recovery Manager: Release 11.2.0.3.0 - Production on Wed Aug 16 15:02:41 2017

Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

connected to target database: DEV (DBID=4028789387)
connected to recovery catalog database

RMAN>

NOW create catalog Run the CREATE CATALOG command to create the catalog. The creation of the catalog can take several minutes. 
If the catalog tablespace is this user's default tablespace, then you can run this command:

RMAN> create catalog;

recovery catalog created

Regiter the database in recovery catalog database;
RMAN> register database;

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