RE: ** optimizer_dynamic_sampling

  • From: A Joshi <ajoshi977@xxxxxxxxx>
  • To: "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>, Brandon.Allen@xxxxxxxxxxx
  • Date: Fri, 26 Jun 2009 17:34:05 -0700 (PDT)

   Thanks. I mean if there are statistics already on the table : then : what is 
the need to do more sampling : is it to take care of changes to the table since 
the statistics were gathered. And is it not a overhead. So would this benefit 
only cases where the table data changes a lot? 
Another question is does this affect in any way  the automatic gather of 
statistics done by job GATHER_STATS_JOB in dba_scheduler_jobs. IS there a way 
to disable it using dba account or can it be disabled as SYS only.  
Apart from setting optimizer_dynamic_sampling=1 and disabling GATHER_STATS_JOB  
: do I need to do any disable to have control over statistics. Thanks 

--- On Fri, 6/26/09, Allen, Brandon <Brandon.Allen@xxxxxxxxxxx> wrote:

From: Allen, Brandon <Brandon.Allen@xxxxxxxxxxx>
Subject: RE: ** optimizer_dynamic_sampling
To: "ajoshi977@xxxxxxxxx" <ajoshi977@xxxxxxxxx>, "oracle-l@xxxxxxxxxxxxx" 
Date: Friday, June 26, 2009, 5:28 PM

The sampling levels are described here:
I haven’t had any problems with auto_sample_size in 10g, but I’ve heard rumors 
that it’s much better/faster in 11g.  Another big change to keep in mind is 
that in 10g histograms will be gathered by default.

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