Re: wait time is huge compared with cpu time

Alex.

As I imagine you'll find on p. 215 of Cary's book (I don't have my copy with me), let's say you have 5000 sessions, all waiting for something for an hour. That's 5000 hours of wait time in one hour. The total wait time isn't based on how many CPUs you have, it's based on how many sessions are waiting for how long.

Now please go buy Cary's book. You don't really need it to answer this question, but it will answer a lot more that you're going to have.

--Terry

  Hi

  I have a HP-UX Server running Oracle 8.1.7.4, there are 6 CPUs.

  I have a statspack report which shows this (2 hours interval)

                  Snap Id     Snap Time      Sessions
                  ------- ------------------ --------
   Begin Snap:        143 20-Jul-06 02:31:02      453
     End Snap:        167 20-Jul-06 04:31:06      453 
      Elapsed:                 120.07 (mins)


  Top 5 Wait Events 
  ~~~~~~~~~~~~~~~~~                                             Wait     % Total
  Event                                               Waits  Time (cs)   Wt Time
  -------------------------------------------- ------------ ------------ -------
  latch free                                      3,573,965    6,945,555   99.25
  log file sync                                     122,691       30,316     .43
  log file parallel write                           146,604       18,685     .27
  SQL*Net more data to client                       522,539        1,762     .03
  db file sequential read                            10,923          534     .01 


  Statistic                                    Total   per Second    per Trans 
  --------------------------------- ---------------- ------------ ------------
  CPU used by this session                 2,990,059        415.1         27.6
  CPU used when call started               2,423,510        336.4         22.4

  I was wondering how can we get over 69000 seconds waits in 2 hours with 6 CPUs? That is much larger than

  3600seconds * 6CPUs * 2hours

  TIA   Alex

--

http://www.freelists.org/webpage/oracle-l Received on Fri Jul 21 2006 - 18:47:29 CDT