I am working on a LAN application.

What is the best way to handle multiple users accessing the
same records at once?

1. Do I lock the record when the user navigates to it, therefore
ensuring that the record is available, but keeping everyone else
out indefinitly?

2. Try to lock the record when the user starts editing, and possibly
pop up an error message if the record in use?

3. Try to lock the record when the user clicks Save, and possibly
pop up an error message if the record in use, and forcing the user
to either wait, or discard all the changes?

4. Or, .... what eles can I do?

Thanks