OFL at tip 136 allowed you to determine Who has What files open.

The NET FILE command shows the names of all open shared files on your server and the number of file locks. You can use NET FILE to close individual files and release the locks.

The command syntax is:        net file \[id \[/close\]\]

 Parameter   D e s c r i p t i o n 
 none   Show all open files and locks. 
 id   The identification number, returned by the net file command. If you type net file id, a formated response is displayed. 
 /close   Closes an open file id and releases locked records. Type this command from the server where the file is shared.