Not able to connect as rman catalog "RMAN-04004: error from recovery catalog database: ORA-12154: TNS:could not resolve the connect identifier specified"

If you have created catalog user and you want to connect to rman with that user and you are getting the following error-

RMAN-04004: error from recovery catalog database:
ORA-12154: TNS:could not resolve the connect identifier specified

see below errors--

rman catalog = catalog/metalog@catdb
Recovery Manager: Release 11.2.0.3.0 - Production on Tue Feb 23 15:02:03 2016
Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-00554: initialization of internal recovery manager package failed
RMAN-04004: error from recovery catalog database: ORA-12154: TNS:could not resolve the connect identifier specified

You are trying with connect identifier on same machine on which you have database like @catdb in this command.

Action - Don't use @catdb because if you are using same server to connect there is no need to give connect identifier.

export ORACLE_SID=catdb

-bash-4.1$ rman catalog = catalog/metalog

by giving this you will easily connect to your rman.

If you are trying to connect to catalog database on different host then you have to create tns entry in tnsnames.ora file .

like  ----

catdb =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = hostname )(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SID = DB_NAME)