Oracle 事件监控

SELECT   b.SID,
         DECODE (b.username,NULL, SUBSTR (b.program, 18),b.username) username,
         a.event,
         a.total_waits ,
         a.time_waited ,
         a.average_wait, a.max_wait
FROM v$session_event a, v$session b
WHERE b.SID = a.SID
ORDER BY 1, 4;