Oracle RMAN backup script returns error "Error: 13: Permission denied" on NFS share

Issue

• RMAN backup was ran and the storage that stored the RMAN file is a NFS mounpoint. Rman backup script executed and returned the following error :-

ORA-19870: error while restoring backup piece /srv/bckora8/rman/ebsamal/EBSAMAL_0_tqul387s_1_1_1028759804
ORA-27091: unable to queue I/O
ORA-27041: unable to open file
Linux-x86_64 Error: 13: Permission denied
Additional information: 3 

• Oracle support claims that it is a OS problem.
• NFS (Netapp Vendor) support also check and claim that NFS share has no problem.