How do I identify the locked table?

I have a problem with a lock that isn't getting released. I have figured out which O/S process is causing the problem based on the session ID. Is there also some way to identify the resource (table) that is being locked. So far I have only figured it out by trial and error using the list of tables being accessed by the offending session and the overlapping list of tables accessed by the sessions that are locked out. I'm looking for something along the lines of:

   select table_name from resource_table where resource_id = nnnn;

        Appreciate any help via E-mail asap!!!
               thanks,
                jim