Getting error while drd runcmd swremove

[drd runcmd swremove iss]

How to solve this:
I instllaed package sucessfully using drd runcmd swinstall,while removing using drd runcmd swremove I am getting this error as well as I am not able to do drd umount:
ERROR: Unmounting the file system fails.
- Unmounting the clone image fails.
- The "umount" command returned "1". The "sync" command returned "0". The error messages
produced are the following: "umount: cannot unmount /dev/drd00/lvol7 : Device busy
umount: return error 1.
"
* Cleaning Up After Command Execution On Inactive System Image failed with 1 error.

[drd runcmd swremove iss]

one more observation:
# bdf /dev/drd00/lvol7
Filesystem kbytes used avail %used Mounted on
/dev/drd00/lvol7 6160384 518328 5289428 9% /var/opt/drd/mnts/sysimage_001/var