ORA-12154: TNS:could not resolve the connect identifier specified when Exec Rman Duplicate

Symptom:    

The Error details are blow:
We run below on target DB hosts:

RMAN>  connect target sys/****@testdb
connected to target database: testdb (DBID=1516071651)
RMAN>  connect auxiliary sys/*****@testdbaux
connected to auxiliary database: testdbaux(not mounted)
RMAN> DUPLICATE TARGET DATABASE  TO 'testdbaux' FROM ACTIVE DATABASE ;

RMAN-00571: ===========================================================

RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============

RMAN-00571: ===========================================================

RMAN-03002: failure of Duplicate Db command at 07/30/2018 00:53:16

RMAN-05501: aborting duplication of target database

RMAN-03015: error occurred in stored script Memory Script

RMAN-03009: failure of backup command on ORA_DISK_1 channel at 07/30/2018 00:53:16

ORA-17629: Cannot connect to the remote database server

ORA-17627: ORA-12154: TNS:could not resolve the connect identifier specified

ORA-17629: Cannot connect to the remote database server

Diagnosis:

  On Target testdb hosts,   tnsping testdb and testdbaux are both fine.
  sqlplus into each other on both side are working well. tnsnames.ora are set correctly on both side.
  Similar issue recorded on oracle community link

  It turns out rman duplicate will run sessions from testdbaux hosts to connect to testdb target hosts
  It error out as we forgot to add TNS entries in testdbaux DB GRID home tnsnames.ora . The rman duplicate may use Grid home TNS  entries which confuses people

Solution:

   Add same TNS entries for both target and aux  DB GRID home tnsnames.ora