RMAN-06172: no AUTOBACKUP found or specified handle is not a valid copy or piece

RMAN> restore controlfile from '/mount/nfs/mydb/20141213/control_132343_gdfgvdf.bak';

Starting restore at 20.12.2014 07:28
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=235 device type=DISK

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of restore command at 12/20/2014 06:28:43
RMAN-06172: no AUTOBACKUP found or specified handle is not a valid copy or piece


Check the alert log :

Alert log content:
==============

Sat Dec 20 07:28:43 2014
WARNING:NFS mount of file /mount/nfs/mydb/20141213/control_132343_gdfgvdf.bak on filesystem /mount/nfs/mydb/20141213/control_132343_gdfgvdf.bak done with incorrect options
WARNING:Expected NFS mount options: rsize>=32768,wsize>=32768,hard,
WARNING:NFS mount of file /mount/nfs/mydb/20141213/control_132343_gdfgvdf.bak on filesystem /mount/nfs/mydb/20141213/control_132343_gdfgvdf.bak done with incorrect options
WARNING:Expected NFS mount options: rsize>=32768,wsize>=32768,hard,


Solution: Mount the nfs mount point with proper options . 

As per oracle metalink below are the valid options:

In the table below 

• Binaries is the shared mount points where the Oracle Home and CRS_HOME is installed.
• Datafiles includes Online Logs, Controlfile and Datafiles
• nfsvers and vers are identical on those OS platforms that has nfsvers.  The ver option is an alternative to the nfsvers option. It is included for compatibility with other operating systems
• Please note that the mount options on each of the following cells are applicable only to those type of files listed in the column heading.
• For RMAN backup sets, image copies, and Data Pump dump files, the "NOAC" mount option should not be specified - that is because RMAN and Data Pump do not check this option and specifying this can adversely affect performance.

* NFS mount option “forcedirectio” is required on Solaris platforms when mounting the OCR/CRS files when using Oracle 10.1.0.4 or 10.2.0.2 or later (Oracle unpublished bug 4466428) 

** AIX is only supported with NAS on AIX 5.3 TL04 and higher with Oracle 10.2.0.1 and later
*** NAS devices are only supported with HPUX 11.23 or higher ONLY 

Due to Unpublished bug 5856342, it is necessary to use the following init.ora parameter when using NAS with all versions of RAC on Linux (x86 & X86-64 platforms) until 10.2.0.4. This bug is fixed and included in 10.2.0.4 patchset.
filesystemio_options = DIRECTIO

Single Instance (non-RAC)