Re: An ancient mystery

  • From: "Andrew Kerber" <andrew.kerber@xxxxxxxxx>
  • To: oracledba.williams@xxxxxxxxx
  • Date: Thu, 20 Nov 2008 21:51:36 -0600

Is it possible someone gathered stats on the table, so the query went into
CBO mode, and came up with a bad plan?  Other than that, as I recall about
the only thing that can go wrong with RBO is a bad index.  But I would have
expected that to throw an error message.

On Thu, Nov 20, 2008 at 9:05 PM, Dennis Williams <
oracledba.williams@xxxxxxxxx> wrote:

> List,
> The situation:
> Oracle 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

Andrew W. Kerber

'If at first you dont succeed, dont take up skydiving.'

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