Re: Data Warehouse and DB Block Buffers

Thanks for the reply. We have DB block buffers set to 500MB and are using PQO. The stripe size in Oracle is set to 16K though the raid stripe is set to 64K. (recommended by HP) Can the Oracle multi block read count be set to 64k?

We have read tablespaces on RAID5, indexes on RAID1/0 and logs on RAID1.

My next question is UNIX buffer cache. It is set to 200MB. Would Oracle benefit from UNIX cache (using jfs filesystems)? I would think it would add unnecessary overhead since Oracle has it's own buffers. What about "Direct IO" on HPUX?

In article <6kv1cs$qvp$1_at_nnrp1.dejanews.com>,   bpage_at_my-dejanews.com wrote:
>
> In article <6kuqb6$g2e$1_at_nnrp1.dejanews.com>,
> rad_at_earthling.net wrote:
> >
> > I'm a UNIX systems guy, not a DBA. That said..
> >
> > Does a data warehouse take much advantage of db block buffers?
>
> YES!!! OLAP is a lot diffent than OLTP. OLAP normally uses much more data
at
> a time to sum, average, calculate change differences, and other time
dependant
> calculations. The more data it can bring in at a time the better off you
are.
> And if you have not yet created the database or you can recreate it, make
the
> db blocksize at least 16k or 32k. The more data brought in at once the
> better.
>
> > If it is
> > mostly doing full tablescans that are not repetitive from one job to the
> next,
> > will Oracle be reusing any data in the db block buffers? If a DW does
> utilize
> > db buffers, how so?
> >
> Sometimes yes and sometimes no, it depends on how the database is designed.
> One place where it really helps is by keeping the support tables in memory
> (table caching helps with this too). Where you get the big bang for your
buck
> here is if they do a lot of calculating on the fly, it really drops your
i/o.
>
> > Also, when loading data into a single table on a DW, will the data be
placed
> > contigously physically? That is, will full tablescans take advantage of
> read
> > ahead cache on a high end disk array?
> >
>
> If you are loading it into a "clean" area, yes. Something else that makes a
> big difference is to index the crap out of the database. It will slow down
> the loading, but it will get rid of theose full table scans.
>
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-----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/ Now offering spam-free web-based newsreading Received on Mon Jun 01 1998 - 16:30:10 CDT