Re: understanding OPT_ESTIMATE and SCALE_ROWS !!

From: Stefan Koehler <>
Date: Fri, 17 Feb 2017 10:37:59 +0100 (CET)
Message-ID: <>

Hey Prem,
just in addition to what Chris said. Oracle does these things all the time (on-the-fly) - keyword "Cardinality / Statistics Feedback".

Just have a look into view v$sql_reoptimization_hints.

Best Regards
Stefan Koehler

Independent Oracle performance consultant and researcher Website:
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> Prem Khanna J <> hat am 17. Februar 2017 um 02:40 geschrieben:
> Hi Chris - Thanks for your reply.
> >>The other thing you can do without a SQL profile is take the hint text and add it directly to the SQL ...
> Yes, would like to fix the problem (the root cause) without using profiles as far as possible. Want to avoid the issues like the profile does not
> work later in a point of time when my data volume or distribution changes . So trying to understand what/how exactly this OPT_ESTIMATE does it
> stuff.
> Hi Marko - Thanks for your reply.
> >>
> I went thro' this blog already. Looks like this is the only article that explains this stuff :-) Sso , what I understand is : histograms (on skewed
> columns) + estimate_percent
> 100% (though not practically possible everytime) or AUTO is going to give a better insight to optimizer. right ? Looks like , that's what tuning
> advisor does most of
> the time ... gives better detailed abt data and it's distribution to the CBO. Please correct me , if I am wrong.
> Regards,
> Prem

Received on Fri Feb 17 2017 - 10:37:59 CET

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