Hulk when you unmount a filesystem you are asking the OS to remove a branch from the filesystem tree. If the branch is still used (someone have a process with a "current working directory" inside the branch) the OS will refuse to unmount the FS (since it's "busy" meaning that someone inside the host is still using the FS).

are you backing this up with TSM client ? Ask your SA to look with "fuser" ...see if TSM client still has a handle open on that mount point.

yes we are backing up with TSM client. from above post I could understand that the issues is with the back up server, not with the bcv dev.

what is this fuser?

http://en.wikipedia.org/wiki/Fuser_(Unix)

pretty good stuff...