Re: Data Buffer Cache

This is indeed true, provided you're prepared to undergo continuous checkpointing. If you have an SLA demanding signed, sealed and delivered instance recovery times, fair enough. But otherwise, *anything* that induces checkpointing when its not needed has got to be a dubious idea at best.

I tend to suggest making sure these parameters are either not set, or set to ridiculously high levels so they don't have any practical effect.

Unless you need the guaranteed recovery times, of course.

Regards
HJR "Richard Foote" <richard.foote_at_bigpond.com> wrote in message news:QyPh9.35013$g9.98743_at_newsfeeds.bigpond.com...
> Hi Howard and all,
>
> I think I'm missing something here or maybe it's somewhat out of the scope
> of this discussion (although I don't think it is).
>
> This concept of sizing redo logs in order to control the behaviour of
> checkpointing. I have no problem with it pre 8i. However it's all somewhat
> irrelevant (or it should be) since the changes in behaviour of the buffer
> cache and the introduction of the fast_start_io_target parameter in 8i
(and
> fast_start_mttr_target in 9i).
>
> By setting these parameters appropriately, the sizing of redo logs in
order
> to control checkpoint behaviour is no longer an issue per se. Oracle will
> continually post the DBWR to ensure that dirty blocks preventing these
> targets from being met are flushed to disk.
>
> The advantages of course being *predicable* instance recovery times
> regardless of size of redo logs or when the last checkpoint may have
> completed and an *even* load at all times, no longer there being spikes of
> activity as Oracle desperately tries to complete a checkpoint.
>
> I just think it's a point worth mentioning ...
>
> Cheers
>
> Richard
> "Howard J. Rogers" <howardjr2000_at_yahoo.com.au> wrote in message
> news:3d878a16_at_dnews.tpgi.com.au...
> > I also tell them of the database in Queensland that produces a 500M
> archive
> > every 7 minutes.
> >
> > I flatter myself that people don't come out of the classroom until
they've
> > got as a complete a picture as it's possible to paint in the time
allowed.
> > If you have to switch that frequently, so be it. Just be aware of the
> costs
> > involved. And if you can avoid switching that frequently, it's generally
a
> > good idea to do so, bearing in mind the further potential costs in
> instance
> > recovery scenarios.
> >
> > The bottom line I give them is: size your logs so that you end up
> switching
> > (and hence checkpointing) at a rate you are happy with.
> >
> > Regards
> > HJR
> >
> > "Sybrand Bakker" <gooiditweg_at_sybrandb.demon.nl> wrote in message
> > news:t2oeouk7kk8kugc5m2b3c4vlij4jipr61a_at_4ax.com...
> > > On Tue, 17 Sep 2002 19:12:01 +1000, "Howard J. Rogers"
> > > <howardjr2000_at_yahoo.com.au> wrote:
> > >
> > > >I also tell them of the 'one switch per hour' school of DBAing, so
they
> > get
> > > >both sides.
> > >
> > > So what if you often have 250M redolog in less than 30 minutes?
> > > (I'm not joking)
> > >
> > >
> > > Regards
> > >
> > >
> > > Sybrand Bakker, Senior Oracle DBA
> > >
> > > To reply remove -verwijderdit from my e-mail address
> >
> >
>
>
Received on Tue Sep 17 2002 - 23:13:41 CDT