How to unmount a online / mounted VXFS on 5.0 MP3

You may have encountered this

# umount -f /opt/app/oracle
UX:vxfs umount: ERROR: V-3-26360: file system /opt/app/oracle has been mount locked

Taken from the symantec support site - http://seer.entsupport.symantec.com/docs/313851.htm

Details:
Storage Foundation 5.0MP3 introduced a new feature called VxFS filesystem lock which disallows accidental unmounts when the file system resource is online. New umount option mntunlock is used to clear the lock and then unmount the filesystem. The offline script for the Mount resource will use this new option.

How to check if the filesystem is locked by VCS:
# mount -v | grep mntlock

Sometimes, it may be necessary to unmount a mount locked filesystem. This is for cases where VCS service groups having DiskGroup resources configured with UnMountVolumes attribute set and the volumes are mounted outside of VCS control (this is not very common). Use the VxFS umount command for Solaris and vxumount command for Linux to manually unmount the file system

Solaris:
# /opt/VRTS/bin/umount -o mntunlock=VCS

Linux:
# /usr/lib/fs/vxfs/umount -o mntunlock=VCS

Example:
# mount -v | grep mntlock
/dev/vx/dsk/oracledg/oracle on /opt/app/oracle type vxfs read/write/setuid/devices/mincache=direct/convosync=direct/delaylog/largefiles/qio/ioerror=mwdisable/mntlock=VCS/dev=46c2ee0 on Mon Sep 15 18:28:18 2008
# /opt/VRTS/bin/umount -o mntunlock=VCS /opt/app/oracle