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Re: DB Buffer Cache Size

From: Joel Garry <>
Date: 23 Aug 2004 16:57:22 -0700
Message-ID: <>

"Howard J. Rogers" <> wrote in message news:<4128f1c0$0$3928$>...
> It's funny: the Oracle Performance Tuning course has for years been drumming
> into people (correctly, IMO) the order of events: Design, Application,
> Memory, I/O, Contention, Operating System. Any other order of events is
> likely to result in 'loop tuning', where you fix problem A, move onto
> problem B, and find that fixing problem B has re-blown problem A.
> No doubt it's lucrative for the consultant. But it's not efficient.

It's not efficient if you are looking at the whole life-cycle from the beginning, but that is not the problem being solved when you go in to fix a messed-up system, is it? The efficiency must be measured from the correct starting point, and Design is not the starting point in a running system. If your tire goes flat in the middle of Wisconsin do you ship the Nissan back to Japan? How efficient is that? (Some Nissan sports cars have an apparent design defect that causes premature wear on tires).

> >> The reason we have experts is because the problem is a complex one. And
> >> no, just throwing more memory at the problem does NOT make it go away.
> >
> > Hmmm, consider this. I had a client last month will a REALLY
> > messed-up database and it was HEAVILY I/O bound (85% read waits).
> > Instead of charging $100k to fix the mess I replaced the disks to
> > high-speed RAM-SAN (solid-state disk)for only $40k. The system ran
> > 15x faster, in less than 24 hours, and the client was VERY happy.
> > Granted, it's not elegant, but hey, why not throw hardware at lousy
> > code if it's cheap and fast?
> Because he's now just bought hardware he doesn't actually need. I wish I
> could be so cavalier with other people's money...

It's not pretty cavalier to spend even more money doing a "correct" fix?

> I'm surprised you let your trade secrets out this readily, however. No-one
> need ever call you in again. Much cheaper and quicker to call the hardware
> vendor in.
> >> People talk a lot of nonsense quite often, don't they?
> >
> > Like it or not, disk will soon be as obsolete as drums! I remember
> > when 1.2 gig of disk costs $250k and I can now get 100 gig of SSD for
> > only $110k.
> >
> > I have several fully-cached clients (some using SSD and other with a
> > huge KEEP pool), and it runs great. . .
> >
> > I hear rumors that Redwood is working on a solid-state Oracle in a
> > future release where the caches will disappear complete, so let's
> > enjoy this discussion while we still can!
> I think we're addressing different audiences, Don. You seem to have the
> money-no-object end of town all sewn up. I'll stick with the ordinary folk.

Speaking as someone who deals more with the low end, I have to agree with Don, when costs are evaluated, quick-and-cheapness wins. I agree with you, the view should be long term, cheapness has its own costs, but the US reality is quarterly accounting. Efficiency for its own sake is not necessarily an ideal solution.


-- is bogus.
"Whenever you have an efficient government you have a dictatorship."
Harry S Truman, Lecture at Columbia University, 28 Apr. 1959
Received on Mon Aug 23 2004 - 18:57:22 CDT

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