-- Copyright 2018 Tanel Poder. All rights reserved. More info at http://tanelpoder.com
-- Licensed under the Apache License, Version 2.0. See LICENSE.txt for terms & conditions.

-- this script uses "ASH math" by John Beresniewicz, Graham Wood and Uri Shaft
-- for estimating the event counts (and average durations):
--   https://www.slideshare.net/jberesni/ash-architecture-and-advanced-usage-rmoug2014-36611678

COL evh_event HEAD WAIT_EVENT for A50 TRUNCATE
COL evh_graph HEAD "Estimated|Time Graph" JUST CENTER FOR A12
COL pct_evt_time HEAD "% Event|Time"
COL evh_est_total_sec HEAD "Estimated|Total Sec" FOR 9,999,999.9
COL evh_millisec HEAD "Wait time|bucket ms+" FOR A15 JUST RIGHT
COL evh_event HEAD "Wait Event"
COL evh_sample_count HEAD "Num ASH|Samples"
COL evh_est_event_count HEAD "Estimated|Total Waits"

BREAK ON evh_event SKIP 1

SELECT 
    event evh_event
  , LPAD('< ' || CASE WHEN time_waited = 0 THEN 0 ELSE CEIL(POWER(2,CEIL(LOG(2,time_waited/1000)))) END, 15) evh_millisec
  , COUNT(*)  evh_sample_count
  , ROUND(SUM(CASE WHEN time_waited >= 1000000 THEN 1 WHEN time_waited = 0 THEN 0 ELSE 1000000 / time_waited END),1) evh_est_event_count
  , ROUND(CASE WHEN time_waited = 0 THEN 0 ELSE CEIL(POWER(2,CEIL(LOG(2,time_waited/1000)))) END * SUM(CASE WHEN time_waited >= 1000000 THEN 1 WHEN time_waited = 0 THEN 0 ELSE 1000000 / time_waited END) / 1000,1) evh_est_total_sec
  , ROUND ( 100 * RATIO_TO_REPORT( CASE WHEN time_waited = 0 THEN 0 ELSE CEIL(POWER(2,CEIL(LOG(2,time_waited/1000)))) END * COUNT(*) ) OVER (PARTITION BY event) , 1 ) pct_evt_time
  , '|'||RPAD(NVL(RPAD('#', ROUND (10 * RATIO_TO_REPORT( CASE WHEN time_waited = 0 THEN 0 ELSE CEIL(POWER(2,CEIL(LOG(2,time_waited/1000)))) END * COUNT(*) ) OVER (PARTITION BY event)), '#'),' '), 10)||'|' evh_graph
FROM 
    dba_hist_active_sess_history
WHERE 
    regexp_like(event, '&1') 
AND sample_time BETWEEN &2 AND &3
AND session_state = 'WAITING' -- not really needed as "event" for ON CPU will be NULL in ASH, but added just for clarity
AND time_waited > 0 
GROUP BY 
    event
  , CASE WHEN time_waited = 0 THEN 0 ELSE CEIL(POWER(2,CEIL(LOG(2,time_waited/1000)))) END -- evh_millisec
ORDER BY
    event
  , CASE WHEN time_waited = 0 THEN 0 ELSE CEIL(POWER(2,CEIL(LOG(2,time_waited/1000)))) END
/

