ORA-00245: control file backup failed; in Oracle RAC, target might not be on shared storage

RAC database backup with RMAN failed with error:

Starting Control File and SPFILE Autobackup at 2015-09-14:23:13:44
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of Control File and SPFILE Autobackup command on Disk channel at 2015-09-14:23:13:45
ORA-00245: control file backup failed; in Oracle RAC, target might not be on shared storage

This is because From 11gR2 onwards, the controlfile backup happens without holding the controlfile enqueue. For non-RAC database, this doesn't change anything. But for RAC database, due to the changes made to the controlfile backup mechanism in 11gR2, any instance in the cluster may write to the snapshot controlfile. Due to this snapshot controlfile need to be visible to all instances. The snapshot controlfile MUST be accessible by all nodes of a RAC database, if the snapshot controlfile does not reside on a shared device error will be raised at the time of RMAN backup while taking snapshot of controlfile. This applies to backing up controlfile using sqlplus / having autobackup of controlfile configured on non shared location.
Solution:
This is a RAC specific configuration issue and the correct configuration is as described below It is changed behaviour which requires that the snapshot controlfile in a RAC environment, is on a shared location.
Check the snapshot controlfile location:

RMAN> show snapshot controlfile name;

Configure the snapshot controlfile to a shared disk :

RMAN> CONFIGURE SNAPSHOT CONTROLFILE NAME TO '+DG01/snapcf_RACDB.f';