Re: Data Buffer Cache

Hi All,
It was a very entertaining and enlightening discussion.....:-)

Cheers,
Ashok

"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 Wed Sep 18 2002 - 01:14:16 CDT