Re: segment monitoring, stats, histograms

  • From: Wolfgang Breitling <breitliw@xxxxxxxxxxxxx>
  • To: jeremiah@xxxxxxxxxxx
  • Date: Thu, 03 Feb 2005 17:36:13 -0700

In my opinion and experience, NO to all questions

There is an interesting - because kind of flying in the face of standard 
Oracle rhetoric, manifested in 10g by enabling monitoring and regular 
(daily) "stale" statistics gathering as a default during the install - note 
on metalink:

Note:44961.1. Gathering Statistics Frequency and Strategy Guidelines

Of course, I particularly like this quotes:

"Given a production system with predictable, known queries, the 'best' 
execution plan for each statement is not likely to vary over time"

"Given the best plan is unlikely to change, frequent gathering statistics 
has no benefit."


At 05:08 PM 2/3/2005, Jeremiah Wilton wrote:

>I'm working on 9.2.0.4 and considering the 'automated statistics gatherin=
>g' approach.  This involves turning on monitoring for any and all tables =
>that need to ever have stats updated, then periodically running dbms_stat=
>s in gather_stale mode.
>
>How is this working for people?  Does monitoring impact DML operations, a=
>nd if so, how much?
>
>Does this approach make any kind of intelligent decisions about sample si=
>zes and block sampling?
>
>When histograms are present, does this approach always/never/sometimes re=
>generate the histogram with the correct number of buckets?
>
>Does it seem to reliably choose the correct tables to analyze?

Regards

Wolfgang Breitling
Centrex Consulting Corporation
www.centrexcc.com 

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