"ORA-00245: control file backup failed; target is likely on a local file system" Backup fails on oracle 11.3 RAC database

We have 8 node Rac cluster. nothing is shared .
On a 8 node RAC database we were occasionally facing issue with RMAN backup.
released channel: CH3
released channel: CH4
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of resync command on default channel at 09/10/2013 22:03:09
ORA-00245: control file backup failed; target is likely on a local file system

Recovery Manager complete.
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of resync command on default channel at 09/10/2013 22:03:09
ORA-00245: control file backup failed; target is likely on a local file system

 rman target/

Recovery Manager: Release 11.2.0.3.0 - Production on Tue Sep 10 23:01:50 2013

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

connected to target database: RAC (DBID=XXXXXXXX)

Before ---

RMAN> show snapshot controlfile name;

using target database control file instead of recovery catalog
RMAN configuration parameters for database with db_unique_name RAC are:
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '<oracle_home_dbs>/snapcf_RAC01.f';

RMAN>

Thus in different instances I found the value is different as snapcf_rac02.f/snapcf_rac02.f ...rac08, also noticed "#default" at the end.

The issue is intermittent and does not appear every time, and so we are not sure if this is actually some issue with configuration.

Reason:-
Oracle [Support Note ID 1472171.1] says that snapshot control file should be on shared location.


After Taking action -
RMAN> show snapshot controlfile name;

using target database control file instead of recovery catalog
RMAN configuration parameters for database with db_unique_name RAC are:
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '+DATA/RAC/datafile/snapcf_RAC.f';

RMAN>

So at the place of making it on shared location we just gave it a common name, by just giving following command from any one node.

RMAN> CONFIGURE SNAPSHOT CONTROLFILE NAME TO '+DATA/RAC/datafile/snapcf_RAC.f';

After setting snapshot controlfile to Shared location (diskgroup) all the backups are successful.