Re: OPTIMIZER_DYNAMIC_SAMPLING Level 11

  • From: Martin Preiss <mtnpreiss@xxxxxx>
  • To: Christian Antognini <Christian.Antognini@xxxxxxxxxxxx>
  • Date: Fri, 12 Dec 2014 11:09:29 +0100

Hi Chris,
thank you for the additions. I saw some result cache answers for the DS_SVC queries - but did not expect the mentioned "statistics repository" to be just a cache layer.
Good to hear that you are writing a paper covering the topic: I am sure it will answer lots of questions. 

Regards

Martin

Am 12.12.2014 um 09:41 schrieb Christian Antognini:

Hi Martin


is there an interface to check the persisted information?

ADS doesn't store information into the DD. It only caches the result of the DS 
to save time during the next parses. For that purpose the optimizer uses two 
caches: 1) the result cache 2) another internal cache that, AFAIK, is not 
externalized.


My impression is that the documentation is not very verbose in describing the
details - so I hope that you can shed some light on the affair.

As soon as the paper I'm writing for the next Hotsos Symposium (see 
http://www.hotsos.com/sym15/sym_speaker_antognini.html for the abstract of the 
presentation) will be available, I hope that it will answer lot of questions 
that aren't covered from the official documentation.


HTH
Chris Antognini

Troubleshooting Oracle Performance, Apress 2008/2014
http://top.antognini.ch




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