SQL Server Performance

More about Update Statistics

Discussion in 'Performance Tuning for DBAs' started by Luis Martin, Jun 26, 2003.

  1. Luis Martin Moderator

    I run the Chappy's SQL [<img src='/community/emoticons/emotion-1.gif' alt=':)' />] (from Thomas problem) and found the following:<br /><br />All statisctic created by mi were actualiced on time, I mean once a week.<br /><br />But there is some statistics begin with _WA_sys_xxxxxx witch has size NULL and LastUpdate NULL.<br /><br />I review the maitenance job <br /><br />(EXECUTE master.dbo.xp_sqlmaint N'-PlanID 380744FF-36FE-11D7-B2E4-006067738CC3 -Rpt "D:MSSQL7LOGUpdate Statisctics0.txt" -WriteHistory -UpdOptiStats 100 ')<br /><br /> and I don't know why those statistics was ignored.<br /><br />Using SQL Analizer, Manage Statistics, I find those statisctics and update manually.<br />Then run Chappys's SQL [<img src='/community/emoticons/emotion-2.gif' alt=':D' />] and now are updated.<br /><br /><br />The question is: why the maitenance job dos not work for every statistics?<br /><br />Luis Martin
  2. bradmcgehee New Member

    This is a good question, and I wish I had an answer. I checked one of my large databases, and it had over 100 rows where the statistics were listed as NULL. My guess, and this is only a guess, is that SQL Server doesn't really need these statistics, and that is why they were never created. Of course, then why did SQL Server add the row in the first place? I don't know. I don't think this is a very important issue.

    It might be interesting to delete all of these rows, then watch over time to see if SQL Server recreates them. This may or may not provide a clue to what is going on.

    Brad M. McGehee, MVP
  3. Luis Martin Moderator

    Thank Brad.

    I will do that, if I have some changes I'll put the conclusion in the forum.


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