Re: An ancient mystery

  • From: "Niall Litchfield" <niall.litchfield@xxxxxxxxx>
  • To: oracledba.williams@xxxxxxxxx, "Oracle Discussion List" <oracle-l@xxxxxxxxxxxxx>
  • Date: Fri, 21 Nov 2008 08:41:04 +0000

Is partitioning or another feature that implies the cost based
optimiser in use?

On 11/21/08, Dennis Williams <oracledba.williams@xxxxxxxxx> 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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Niall Litchfield
Oracle DBA
http://www.orawin.info
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