who is locking my tables ?

SELECT owner || '.' || object_name obj,
         oracle_username || ' (' || s.status || ')' oruser,
         os_user_name osuser,
         machine computer,
         l.process unix,
         '''' || s.sid || ',' || s.serial# || '''' ss,
         r.name rs,
         TO_CHAR (s.logon_time, 'yyyy/mm/dd hh24:mi:ss') time
    FROM v$locked_object l,
         dba_objects o,
         v$session s,
         v$transaction t,
         v$rollname r
   WHERE     l.object_id = o.object_id
         AND s.sid = l.session_id
         AND s.taddr = t.addr
         AND t.xidusn = r.usn
ORDER BY obj,osuser, ss