使用V$ACTIVE_SESSION_HISTORY视图，查看消耗资源的sql

--查找最近一分钟内，最消耗CPU的sql语句	
SELECT sql_id, 
	count(*), 
	round(count(*) / sum(count(*)) over(), 2) pctload
FROM V$ACTIVE_SESSION_HISTORY
WHERE sample_time > sysdate - 1 / (24 * 60)
	AND session_type <> 'BACKGROUND'
	AND session_state = 'ON CPU'
GROUP BY sql_id
ORDER BY count(*) desc;

--查找最近一分钟内，最消耗I/O的sql语句
SELECT ash.sql_id,
	count(*)
FROM V$ACTIVE_SESSION_HISTORY ASH,V$EVENT_NAME EVT
WHERE ash.sample_time > sysdate -1/(24*60)
	AND ash.session_state = 'WAITING'
	AND ash.event_id = evt.event_id
	AND evt.wait_class = 'USER I/O'
GROUP BY ash.sql_id
ORDER BY count(*) desc;

--查找最近一分钟内，最消耗CPU的session
SELECT session_id,
	count(*)
	FROM V$ACTIVE_SESSION_HISTORY
WHERE session_state = 'ON CPU'
	AND sample_time > sysdate -1/(24*60)
GROUP BY session_id
ORDER BY count(*) desc;

--查找最近一分钟内，最消耗资源的sql语句
SELECT ash.sql_id,
	sum(decode(ash.session_state,'ON CPU',1,0)) "CPU",
	sum(decode(ash.session_state,'WAITING',1,0)) -
	sum(decode(ash.session_state,'WAITING',decode(en.wait_class,'USER I/O',1,0),0)) "WAIT",
	sum(decode(ash.session_state,'WAITING',decode(en.wait_class,'USER I/O',1,0),0)) "IO",
	sum(decode(ash.session_state,'ON CPU',1,1)) "TOTAL"
	FROM V$ACTIVE_SESSION_HISTORY ASH,V$EVENT_NAME EN
WHERE SQL_ID is not null and en.event#=ash.event# and ash.sample_time > sysdate -1/(24*60)
GROUP BY ash.sql_id
ORDER BY sum(decode(ash.session_state,'ON CPU',1,1)) desc;

--查找最近一分钟内，最消耗资源的session
SELECT ash.session_id,
	ash.session_serial#,
	ash.user_id,
	ash.program,
	sum(decode(ash.session_state,'ON CPU',1,0)) "CPU",
	sum(decode(ash.session_state,'WAITING',1,0)) -
	sum(decode(ash.session_state,'WAITING',decode(en.wait_class,'USER I/O',1,0),0)) "WAITING",
	sum(decode(ash.session_state,'WAITING',decode(en.wait_class,'USER I/O',1,0),0)) "IO",
	sum(decode(ash.session_state,'ON CPU',1,1)) "TOTAL"
FROM V$ACTIVE_SESSION_HISTORY ASH,V$EVENT_NAME EN
WHERE en.event# = ash.event# and ash.sample_time > sysdate -1/(24*60)
GROUP BY ash.session_id,ash.user_id,ash.session_serial#,ash.program
ORDER BY sum(decode(ash.session_state,'ON CPU',1,1));