Re: redo logs tuning?

"Frank" <frankbo_at_interaccess.nl> wrote in message news:8p2gnj$kn4$1_at_porthos.nl.uu.net...
> I beg to have a different opinion:
> set log_checkpoint_interval so high, that no checkpointing will occur,
 other
> than during log switches. This is also the reason you want the timeout set
> very high,
> or disable it completely.
> Check the tuning manual on tuning check points (Ch 15), gents.
>
> As for the size, check how often switching occurs during "normal"
 operation
> of the database (see your alert log file). Aim for 1 or 2 per hour.
>
> log_checkpoint_interval is in OS blocks (usually 512byte), indeed.
>
> Open to other opinions - always enjoy a good discussion!
>
> --
> Frank

I agree Frank: the best performance option is *never* to checkpoint during the day, and to have one mammoth I/O fest at the dead of night when no-one gives a damn. However, the corollary of that approach is enormous Instance recovery times, and that might not be acceptable to many people. Mean Time to Recover is not something that can lightly be ignored on most systems.

As an aside, the "usually 512byte" is a bit of a whitewash: it really is platform specific, as Steve advises, and his web site (which no self-respecting Performance Tuner can afford to ignore) is entirely correct.

Regards
HJR
> Steve Adams <steve.adams_at_ixora.com.au> schreef in berichtnieuws
> 39b4b9fb.104161686_at_nsw.nnrp.telstra.net...
> > Hi All,
> >
> > No, the units for the log_checkpoint_interval are log blocks. The log
 block size
> > is platform specific. It is often 512 bytes, but by no means always. The
 "Why
> > raw log files?" tip on the Ixora web site contains a table of the log
 block
> > sizes for the most popular platforms.
> >
> > @ Regards,
> > @ Steve Adams
> > @ http://www.ixora.com.au/
> > @ http://www.christianity.net.au/
> > @
> > @ Going to OpenWorld?
> > @ Catch the Ixora performance tuning seminar too!
> > @ See http://www.ixora.com.au/seminars/ for details.
> >
> >
> > On Mon, 4 Sep 2000 19:05:01 +0200, "Sybrand Bakker"
 <postbus_at_sybrandb.demon.nl>
> > wrote:
> >
> > >
> > >"Niall Litchfield" <n-litchfield_at_audit-commission.gov.uk> wrote in
 message
> > >news:8ovunp$2b7$1_at_soap.pipex.net...
> > >> "Sybrand Bakker" <postbus_at_sybrandb.demon.nl> wrote in message
> > >> news:968007698.22997.0.pluto.d4ee154e_at_news.demon.nl...
> > >>
> > >> > Also, don't forget to check log_checkpoint_interval in
 init<sid>.ora.
 In
 the
> > >> > 5M situation it should be 10000.
> > >>
> > >> Presumably for a 2k Block Size? If not how did you arrive at this
 figure?
> > >> --
> > >> Niall Litchfield
> > >> Oracle DBA
> > >> Audit Commission UK
> > >>
> > >>
> > >AFAIK this is in 512-byte units.
> > >
> > >Regards,
> > >
> > >Sybrand Bakker, Oracle DBA
> > >
> > >
> > >
> >
>
>
Received on Wed Sep 06 2000 - 06:59:29 CDT