Re: Really strange performance issue
- From: Andrew Kerber <andrew.kerber@xxxxxxxxx>
- To: "Mark W. Farnham" <mwf@xxxxxxxx>
- Date: Thu, 30 Oct 2014 11:20:39 -0500
For those of you concerned, when experimenting I set the parameter at the
session level while tracking the problem, not the system level. And I have
enabled a baseline for plan stability at least until the bug is fixed. There
appear two be two bugs listed as possible culprits, 13454409 and 8608703, the
former is most likely. Unfortunately the listed patch is only for 11.2.0.3.8,
and we are on 11.2.0.3.11, and I don't see it listed as fixed there. So have
to find out if the ....8 patch will work in ....11. Not to mention verify that
I have the right bug as there are several similar listed.
Sent from my iPad
> On Oct 30, 2014, at 10:17 AM, Mark W. Farnham <mwf@xxxxxxxx> wrote:
>
> As a test to verify what was likely causing the change, that seems reasonable
> and unlikely to yield wrong answers or lose out much in the short haul.
>
> But you’re right on target as regards using a wide scope change as a
> band-aid: some sort of plan stability for the particular statement would be
> much better.
>
> mwf
>
> From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
> Behalf Of Chris Taylor
> Sent: Thursday, October 30, 2014 11:07 AM
> To: Andrew Kerber
> Cc: Mauro Pagano; howard.latham@xxxxxxxxx; oracle-l
> Subject: Re: Really strange performance issue
>
> Wouldn't it be better to attack the problem instead of changing the whole
> "world" by setting the db parameter?
>
> If it's one SQL statement, I'd use a SQL Profile to guarantee the plan that I
> want is used before forcing something at the db level.
>
> Chris
>
> On Thu, Oct 30, 2014 at 10:03 AM, Andrew Kerber <andrew.kerber@xxxxxxxxx>
> wrote:
> And we have a winner. The actual plan must have changed, even though when I
> just ran the explain command it did not. I turned off
> _optimizer_use_feedback and that fixes it. The question is why?
>
> Sent from my iPad
>
> On Oct 30, 2014, at 9:49 AM, Mauro Pagano <mauro.pagano@xxxxxxxxx> wrote:
>
> Does the execution plan change between first and second execution?
> If no the ignore the rest of my message but if yes then an educated guess
> (since we have no other info available) would be "cardinality feedback", you
> can test it setting "optimizer_use_feedback" = false
>
> On Thu, Oct 30, 2014 at 10:42 AM, Howard Latham <howard.latham@xxxxxxxxx>
> wrote:
> Any chance of seeing the Query please?
> --
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>
>
>
>
>
> --
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>
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