I understand what you're saying, but what I would like to see is the results
of actual tests, rather than what appear to be theortical statements.
Howard J. Rogers <dba_at_hjrdba.com> wrote in message
news:1014673079.588197_at_bugstomper.ihug.com.au...
> Recovery time is a combination of the amount of redo to be read, and the
> number of buffers to be recovered. The log_checkpoint parameters only
> affect the first of those. You could imagine, for example, a transaction
> which does expensive inserts and deletes, thus generating reams of redo,
but
> which happened only to affect one or two buffers. Lots of redo to be
read,
> few buffers to be recovered. Conversely, a bunch of updates might
generate
> piddly amounts of redo, but dirty hundreds of buffers (each of which then
> has to be read from disk on subsequent startup, thus generating stacks of
> *datafile* I/O).
>
> You need to set FAST_START_IO_TARGET to limit the number of buffers
> effectively. The_interval and _io_target parameters in tandem do a pretty
> good job of limiting recovery time.
>
> Regards
> HJR
> --
> ----------------------------------------------
> Resources for Oracle: http://www.hjrdba.com
> ===============================
>
>
> "Keith Boulton" <kboulton_at_ntlworld.com> wrote in message
> news:IOxe8.4144$R16.741296_at_news11-gui.server.ntli.net...
> >
> > Keith Boulton <kboulton_at_ntlworld.com> wrote in message
> > news:V24e8.28567$hM6.3678545_at_news6-win.server.ntlworld.com...
> > > failure than in the last 2 hours, so I would go for a checkpoint
timeout
> > in
> > > that case.
> > >
> > Doh!
> >
> > Of course, as someone else pointed out, checkpoint timeout is irrelevant
> to
> > this discussion.
> >
> > I do, however, have a question.
> >
> > Has anyone actually tested the impact of these parameters on recovery
> time?
> >
> > As I said, I have in the past attempted to find a penalty associated
with
> > larger logs, but always with checkpoint interval set high and checkpoint
> > timeout set to 0. While I'm happy enough to believe that my testing
> matches
> > by theorising about limiting factors affecting restart time, I can't
help
> > wondering if there's something I've missed.
> >
> > Any suggestions?
> >
> >
>
>
Received on Tue Feb 26 2002 - 01:28:20 CST
