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Re: Oracle on VMS performance issue

From: Bob Kaplow <kaplow_r_at_eisner.decus.org>
Date: 1998/09/30
Message-ID: <1998Sep30.105016.1@eisner>#1/1

In article <01bde997$eb7ccc80$cd85410c_at_default>, "Phil Cook" <pncook_at_worldnet.att.net> writes:
> You don't want an Oracle block to span multiple stripes. Your real problem
> is how much IO your applications are performing. I would start looking
> at v$sqlarea and the number of IOs. Run explain plans on the top
> statements, and see if these can be tuned.
>
> If you really want to brute force the application with hardware add more
> memory cache at the disk or OS level. Adding more buffer cache to
> the sga may help, look at your buffer hit ratio.

More hardware cache probably won't help. You're describing 3 levels of cache: the application (Oracle), the host system (VIOC?), and the hardware (HS controller?). For the most part, unless outer cache layers are larger than the inner layers, the contents of the outer cache will do nothing more than duplicate the inner layer cache. But the outer cache will never be "hit" because the request will be satisfied by the inner layer. It's mostly a waste of $$$ and can actually slow performance.

One feature we're waiting for is supposed to be in the hs*80 controllers: read ahead cache. For read transactions with locality, and especially for sequential reads, this should help performance.

        Bob Kaplow

SPAM: uce_at_ftc.gov postmaster_at_127.0.0.1 otherwise, I'm not on MARS! Received on Wed Sep 30 1998 - 00:00:00 CDT

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