Blocking Sessions
set pages 200
column module format a20
column program format a20
column username format a15
select s.sid,s.serial#,s.status,p.spid,s.module,s.action,s.program
from v$session s,v$process p
where s.sid in (select session_id from dba_locks where blocking_others='Blocking')
and s.paddr=p.addr
