Typically, if you start a program that resides in a file system and try to unmount the file system, it will fail to unmount. To kill any processes using a file system you can type:
fuser -k /dev/cd0
The above command will kill any processes using the cdrom file system.
To kill all processes using a logical volume / JFS named /dev/lv01 typing:
fuser -k /dev/lv01
If you do not know which logical volume is associated with a file system, type
mount