RMAN-04006: error from auxiliary database: ORA-12528: TNS:listener

[oracle@DB11G dbs]$ rman TARGET sys/*****@DB11G AUXILIARY sys/*****@DB11G_tar

Recovery Manager: Release 11.2.0.3.0 - Production on Mon Feb 20 04:45:31 2017

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

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-04006: error from auxiliary database: ORA-12528: TNS:listener: all appropriate instances are blocking new connections


---------------------->  Solution


[oracle@DB11G admin]$ cat tnsnames.ora
# tnsnames.ora Network Configuration File: /u01/app/oracle/product/11.2.0/db_1/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.

DB11G =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = DB11G.example.com)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = DB11G)
    )
  )
DB11G_tar =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = ASM_DB.example.com)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = DB11G)
    (UR = A)
    )
  )


[oracle@DB11G admin]$ rman TARGET sys/*****@DB11G AUXILIARY sys/******@DB11G_tar

Recovery Manager: Release 11.2.0.3.0 - Production on Mon Feb 20 04:56:25 2017

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

connected to target database: DB11G (DBID=405647198)
connected to auxiliary database: DB11G (not mounted)

RMAN>