Re: inconsistent query performance

Bob,

Reasons for what you see could be many, including: cardinality feedback, bind peeking, dynamic sampling and changes on stats, just to mention the more common reasons for a plan to change.

In cases like this you may want to use tools designed specifically to diagnose SQL. If you have access to MOS you can try SQLT (215187.1) else SQLd360. The latter is free and requires no installation. These days I use only SQLd360. Use either, read the output, and if you cannot figure out the root cause send me the output (if you can) and I will tell you why your plan changes.

Carlos

> On Jan 18, 2017, at 10:28 AM, Stauffer, Bob <RStauffer_at_fult.com> wrote:
>
> Hi all,
>
> Oracle RDBMS EE 11.2.0.4.0 - 64bit
> Red Hat Enterprise Linux 5.11
>
> Any suggestions on how I can troubleshoot a query that performs inconsistently? Sometimes it takes a minute to run and sometimes it takes over an hour. It generally uses one of two explain plans – one fast and one slow. Although it sometimes uses a different plan. I’ve checked the stats and they are up to date. I generally run it in TOAD, but the same problem occurs in SQLPlus, SQL Developer, and other interfaces. It doesn’t matter whether the system is busy or quiet. And it happens within the same session – I can run it one right after another and it will change the plan for each execution.
>
> Any help would be appreciated. I’m a little rusty with Oracle.
>
> Thanks much.
>
> Bob Stauffer
> DBA/Database Developer
>
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