Re: Where best to cache the disk

In article <CyLJrD.D54_at_nntpa.cb.att.com>

           awy_at_wisny.mv.att.com "-yoshida a.w." writes:

> In article <783604402snz_at_sambusys.demon.co.uk>,
> Paul Beardsell <psb_at_sambusys.demon.co.uk> wrote:
> >We are not using raw partitions for our tablespaces.
> >Are we better off caching inside Oracle by using a large SGA
> >and a small Unix disk cache or should we use a small SGA and
> >a large Unix disk cache?
> >
> >I am tempted to assign all our spare memory to the Unix disk
> >cache (by increasing NBUF etc) and to keep the SGA just big
> >enough for DC_* dictionary caching.
> >
> >What say you?
> >
>
> Remember, the Oracle cache is used for all queries - not just those
> on the data dictionary. In general, the most-recently-used algorithm will
> put in cache whatever data was most recently used (or written). Also, why
> invoke the Oracle caching overhead to go to the UNIX file system cache.
> May as well get it out of the Oracle cache in the first place.

But I'm reluctant to cache everything twice. Perhaps I ought to have a small unix cache and a massive Oracle one?

-- 
Paul Beardsell                          SAM Business Systems Ltd
~~~~~~~~~~~~~~                          21 Finn House, Bevenden St,
pbeardsell_at_cix.compulink.co.uk          London, N1-6BN, UK.
psb_at_sambusys.demon.co.uk                (+44 or 0)71 608-2391