Re: Creating Histograms
- From: Wolfgang Breitling <breitliw@xxxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Thu, 22 Jul 2004 16:34:17 -0600
At 01:55 PM 7/22/2004, you wrote:
>take note of how many records you add to relatively *small* tables. 13
>rows added to one of our tables caused hell until we gathered stats
>again (and it took ages for anyone to admit that anything ahd
>changed). That would be 13 rows in the sense of another financial year
>to add to the 2 existing ones - so hardly significant at all :).
Can you give more details on that and why 13 more rows caused hell until
stats were gathered again. What were the execution plans before and after?
Were there histograms involved?
>I guess I'm saying different objects might have different stats needs.
Absolutely.
> >We also don't =
> > collect system stats. I'm hoping to get enough information here to 'have =
> > a meeting' and get all of that changed, the method and rate of =
> > collection.
>
>Test system stats carefully (I'm probably too cautious on this), but
>system stats are likely to make quite a noticeable difference to
>execution times. It is, I'm increasingly convinced, the *right* thing
>to do. It doesn't mean that you may not have adverse effects. Overall
>system stats have been positive for our test financial environment-
>enough so that they get introduced with the next software upgrade that
>is running there - but there has been the odd hiccup.
Whenever you drastically change your operations - going from RBO to CBO,
going from nightly/weekly gather to no-gather with exceptions, going from
no system stats to system stats, or vice-versa is always a big risk and
should be tested very thoroughly.
Regards
Wolfgang Breitling
Centrex Consulting Corporation
www.centrexcc.com
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