Re: CBO influences

Jonathan Lewis wrote:
>
> "Connor McDonald" <connor_mcdonald_at_yahoo.com> wrote in message
> news:43282C72.36FC_at_yahoo.com...
> >
> > In terms of mreadtim < sreadtim, we've encountered this on all databases
> > at our current site that SAN attached as opposed to JBOD. Haven't
> > really got the access to determine whether the SAN is *truly* yielding
> > better multiread IO times than singleread IO, but ultimately we've
> > resorted to
> >
> > - collecting system stats
> > - tweaking mread to just above sread to enable mbrc inclusion for the cbo
> >
>
> That is an interesting tell-tale about what SANs
> are probably good at, and bad at, doesn't it.
>
> Don't share a SAN if you want to run a high
> performance OLTP system - they're not very
> good for small, highly randomised I/Os.
>
> --
> Regards
>
> Jonathan Lewis
>
> http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html
> Cost Based Oracle - Volume 1: Fundamentals
> On-shelf date: Nov 2005
>
> http://www.jlcomp.demon.co.uk/faq/ind_faq.html
> The Co-operative Oracle Users' FAQ
>
> http://www.jlcomp.demon.co.uk/appearances.html
> Public Appearances - schedule updated 4th Sept 2005

I would generalise to SAN's are not good at IO... period

:-)

-- 
Connor McDonald
Co-author: "Mastering Oracle PL/SQL - Practical Solutions"
Co-author: "Oracle Insight - Tales of the OakTable"

web: http://www.oracledba.co.uk
web: http://www.oaktable.net
email: connor_mcdonald_at_yahoo.com


"Semper in excremento, sole profundum qui variat."

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