Oracle locks tree

gistfile1.txt

SELECT LPAD(' ', (level-1)*2, ' ') || NVL(s.username, '(oracle)') AS username,
       s.osuser,
       s.sid,
       s.serial#,
       s.lockwait,
       s.status,
       s.module,
       s.machine,
       s.program,
       s.event,
       s.sql_id
FROM   v$session s
CONNECT BY PRIOR s.sid = s.blocking_session
START WITH s.blocking_session IS NULL;