ORA-27086: unable to lock file - already in use

ORA-27086: unable to lock file - already in use
Cause:

• If NFS is hung
• database is abnormaly shutdown
• Cancle datafile/tempfile creation

You have restated the database still facing the same issue the NFS server still maintains the lock even after a restart database .Then work with your storage admin to manually remove the locks on the files from the NFS side  or you have to Restart NFS Services. You should then be able to restart the database
check nfslock services is running or not
# service nfslock status
rpc.statd (pid  1737) is running...

Stop the services :
# service nfslock stop
# service nfs stop
# service portmap stop
Unmount the nfs
# umount /proc/fs/nfsd

Start services:
# service portmap start
# service nfs start
# service nfslock start
Unmount the nfs
# mount -t nfsd nfsd /proc/fs/nfsd