If I understand your follow-up posts, what I think you really want is to make sure that people know about locks. I'm imagining a case where users A and B have already checked out a jpeg. User A now locks it, and you want to make sure that user B knows, so that he or she doesn't begin editing the jpeg and wasting time and effort.
If that's correct, I recommend two things: first and foremost, communication (not very technical, but very powerful when used consistently); second, you might take a look at the post-lock
repository hook for svn
. You can use that to have emails sent when someone puts a lock on a file.
From the subversion
book:
The post-lock
hook runs after one or more paths have been locked. It is typically used to send email notification of the lock event.