Full procedure
fuser -cu /cdrom (or whatever you named the folder when you mounted it)
If there are no processes on it, there is no need for the next step.
It is possible to get a zombie or process 1 on the cdrom in which case your only good option is to boot.
fuser -cuk /cdrom
kills everything, lists it as it kills it.
Don't be surprised if you lose your session, because its almost always sysadmin that causes this problem.
There should be no need for pfs_umount, but you can try it if you want.
This is not a patching issue, its a sysadmin keeping track of what he or she is doing issue.
If your problem is with pfs_mount, you may start getting NFS errors on the console. They can be safely ignored until you can find a safe window to reboot the machine.
SEP
Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com