Oracle: Session Blocking

From time to time I get a call from the user community at large of people not being able to do anything cause the app is hung up.

It's always been due to a session blocking everyone else. Too bad the application doesn't handle this better on it's own.

Here's a query I use from time to time to see who is blocking.

Select /*+ RULE */ username, v$session.SID, serial#, owner, object_name, object_type, 
       v$lock.TYPE
  FROM dba_objects, v$lock, v$session 
 WHERE object_id = v$lock.id1 AND v$lock.SID = v$session.SID 
       AND owner != 'SYS'
    AND block = 1