Oracle Database Tips by Donald Burleson

System-wide events by time waited

Notice the similarity of the events in these two figures. This demonstrates that either of these scripts will point out the biggest wait events which have occurred on the system.  The time waited sorted report (Figure 5.1, show_system_events.sql) helps to identify the scale or magnitude of difference between these events.  The average time waited sorted report (Figure 5.2, show_system_events2.sql) helps identify the impact on each occurrence.   

After getting a feel for the system by looking at the output from the previous scripts, it is time to start narrowing down the scope. Run session_event_users.sql to see which users are spending the most time waiting, and what events they are waiting for.

* session_event_users.sql

 -- *************************************************

-- Copyright © 2003 by Rampant TechPress

-- This script is free for non-commercial purposes

-- with no warranties.  Use at your own risk.

--

-- To license this script for a commercial purpose,

-- contact info@rampant.cc

-- *************************************************

/* session_event_users.sql */

column USERNAME          format a8

column EVENT             format a30

column SID               format 9999

column AVERAGE_WAIT      format 99999 head "AVG|WAIT"

column TOTAL_WAITS       format 99999 head "TOTAL|WAITS"

column TOTAL_TIMEOUTS    format 9999 head "TOTAL|TIME|OUTS"

column TIME_WAITED       format 999999 head "TIME|WAITED"

column MAX_WAIT          format 99999 head "MAX|WAIT"

column TIME_WAITED_MICRO format 9999999 head "TIME|WAITED|MICRO"

set pagesize 100

select

   b.USERNAME,

   a.*

from

   V$SESSION_EVENT a,

   V$SESSION b

where

See Code Depot

The above book excerpt is from:

Oracle Wait Event Tuning

High Performance with Wait Event Iinterface Analysis 

ISBN 0-9745993-7-9  

Stephen Andert 

http://www.rampant-books.com/book_2004_2_wait_tuning.htm