Re: An ancient mystery

From: Madhu Sreeram <madhusreeram_at_gmail.com>
Date: Sat, 22 Nov 2008 10:02:43 -0600
Message-ID: <6a959ef30811220802o22ada1b4o61cefb67e0e5056e@mail.gmail.com>


Here is a thought.
May be some implicit data conversion is happening? For example, assuming the query involves bind values, passing a number type instead of character type can lead to "unexpected" behavior. The table has possibly grown large enough that you are able to feel the "pain" now.

-Madhu Sreeram

On Thu, Nov 20, 2008 at 9:05 PM, Dennis Williams < oracledba.williams_at_gmail.com> wrote:

> List,
>
> The situation:
>
> Oracle 8.1.7.4 database on Solaris 8 (soon to be upgraded to 10g)
> Rule-based Optimizer
>
> A query which has run for years using an indexed access to a very large
> table (maybe 100 million rows)
> suddenly decides to use a full-table scan, shutting down a critical
> business process.
>
> Then after several hours, it switches back to using the index.
> All concerned claim that nothing changed before or after.
>
> Needless to say the business users are nervous. They think maybe the
> database grew beyond some limit.
>
> Can anyone think of an explanation?
>
> Thanks,
> Dennis Williams
>

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Received on Sat Nov 22 2008 - 10:02:43 CST

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