Re: multiblock read count

From: Michael Bialik <michael_bialik_at_my-deja.com>
Date: Mon, 18 Sep 2000 20:36:25 GMT
Message-ID: <8q5uc7$bo2$1@nnrp1.deja.com>

Hi.

CBO likes it a LOT. It does NOT considers physical I/O, but from it's (CBO's) point of view - the greater the value - the cheaper FULL table scan, so be prepared.

HTH. Michael.

In article <8pu0ub$loc$1_at_nnrp1.deja.com>, Doug Coan <dcoan_at_aegonusa.com> wrote:
> In article <8pqa2s$pjm$1_at_xs4.xs4all.nl>,
> rjn_at_pobox.com (Fidelio) wrote:
> > Hi,
> >
> > I have db_file_multiblock_read_count set to 16 and my block size
> > is 4K. I remember reading somewhere that for optimal performance
> > db_file_multiblock_read_count * db_block_size should be 64 KB.
>
> I agree with this.
>
> >
> > Is this still true for Oracle 8 ? If you have loads of 500 MB
> > tables with 300 MB indexes, does the performance still get a
> > increase by specifying a larger multiblock read count ?
>
> I have seen this set higher and some books are a little ambigiuos
> about the potential for this improving performance. I have seen no
> performance gains when we have done this and would probably recommend
> against it. I'm not sure that the CBO always likes it.
>
> >
> > R
> > --
> > Get tons of referrals - Sign up now ! http://www.refmatrix.com/
> > The Adsenger information resource -

http://www.xs4all.nl/~rob/adsenger.html
> >
>
> HTH......
>
> --
> Doug Coan
> Oracle Certified Professional DBA
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>

Sent via Deja.com http://www.deja.com/
Before you buy. Received on Mon Sep 18 2000 - 15:36:25 CDT