Re: Usage of Multiple Buffer Pools

Sergey Adamenko wrote:
>
> "Connor McDonald" <connor_mcdonald_at_yahoo.com> wrote in message
>
> > I think multiple buffer pools can be useful as a means of spreading out
> > the latching for blocks. The changes in 8i buffer cache management with
> > touch counts (imho) renders the original idea of 'keep' and 'recycle'
> > somewhat obsolete. I think they are better referred to as simply extra
> > pools of memory (although you'd need to tweak a couple of parms to make
> > them all work in the same way)
> >
> > hth
> > connor
> > --
> > =========================
> > Connor McDonald
> > http://www.oracledba.co.uk
> >
> > "Some days you're the pigeon, some days you're the statue"
>
> Well, tables (or segments in general) have their POOL property assigned.
> And their blocks go to the assigned pool. If I'm improperly split my Buffer pool or
> improperly distribute my tables between pools, I can get some memory wasted
> or memory shortage in some pool, which will cause raise in I/O later.
> IMO, this will negate the result of additional latches the pools have.
>
> Thanks,
> Sergey Adamenko.

I'm not suggesting you would allocate objects to pools in a haphazard fashion - but if you got unlucky and two hot objects or part thereof shared a latch, moving one of them to another pool could help.

shared cache latches in 9 on some platforms could possibly even obviate that.

hth
connor

-- 
=========================
Connor McDonald
http://www.oracledba.co.uk

"Some days you're the pigeon, some days you're the statue"