ORA-00494: enqueue [CF] held for too long on NFS mount

DB Version: 11.2.0.1.

NFS was mounted with below options and when we try to backup the controlfile via sqlplus or RMAN. we get the below enqueue error.
no rw,bg,hard,nointr,rsize=32768,wsize=32768,proto=tcp,noac,forcedirectio,vers=3,suid


Backup on NFS mount:
SQL> set time on echo on feedback on
09:49:36 SQL> alter database backup controlfile to '/NFSMOUNT/cloning/control_nfs_09142011.ctl';
alter database backup controlfile to '/NFSMOUNT/cloning/control_nfs_09142011.ctl'
*
ERROR at line 1:
ORA-03113: end-of-file on communication channel
Process ID: 23041
Session ID: 4796 Serial number: 395


10:16:40 SQL>

Alert log:
alter database backup controlfile to '/NFSMOUNT/cloning/control_nfs_09142011.ctl'
Wed Sep 14 10:04:19 2011
Incremental checkpoint up to RBA [0x128.85a78.0], current log tail at RBA [0x128.870c8.0]
Wed Sep 14 10:05:19 2011
Errors in file /icm01/u0001/app/diag/rdbms/icmqc/ICMQC1/trace/ICMQC1_diag_8307.trc (incident=956919):
ORA-00494: enqueue [CF] held for too long (more than 900 seconds) by 'inst 1, osid 23041'
Incident details in: /icm01/u0001/app/diag/rdbms/icmqc/ICMQC1/incident/incdir_956919/ICMQC1_diag_8307_i956919.trc
Wed Sep 14 10:05:25 2011
Sweep [inc][956919]: completed
Sweep [inc2][956919]: completed
Wed Sep 14 10:06:19 2011
Killing enqueue blocker (pid=23041) on resource CF-00000000-00000000 by (pid=8685)
by killing session 4796.395
Wed Sep 14 10:10:39 2011
Killing enqueue blocker (pid=23041) on resource CF-00000000-00000000 by (pid=8321)
by killing session 4796.395
Wed Sep 14 10:16:39 2011
Killing enqueue blocker (pid=23041) on resource CF-00000000-00000000 by (pid=8321)
by terminating the process
Wed Sep 14 10:22:05 2011
Errors in file /icm01/u0001/app/diag/rdbms/icmqc/ICMQC1/trace/ICMQC1_diag_8307.trc (incident=956920):
ORA-00494: enqueue [CF] held for too long (more than 900 seconds) by 'inst 1, osid 23041'
Incident details in: /icm01/u0001/app/diag/rdbms/icmqc/ICMQC1/incident/incdir_956920/ICMQC1_diag_8307_i956920.trc
Wed Sep 14 10:22:35 2011
Sweep [inc][956920]: completed
Sweep [inc2][956920]: completed
Wed Sep 14 10:24:23 2011
Incremental checkpoint up to RBA [0x128.87fc1.0], current log tail at RBA [0x128.88243.0]
Wed Sep 14 10:28:19 2011
Killing enqueue blocker (pid=23041) on resource CF-00000000-00000000 by (pid=8685)
by killing session 4796.395
Wed Sep 14 10:32:39 2011
Killing enqueue blocker (pid=23041) on resource CF-00000000-00000000 by (pid=8321)
by terminating the process

Backup on local disk:


SQL> alter database backup controlfile to '/ora_backup/u0001/control_disk_09142011.ctl';

Database altered.

SQL>

Solution: