Re: Memory Sizing Advice

From: Arne Ortlinghaus <>
Date: Fri, 9 May 2008 15:05:42 +0200
Message-ID: <g01i76$vjo$>

We have a multi purpuse database of about 500 GB on a SAN storing system with about 100 concurrent users. Although we are using many indexes it helped very much to have 20GB of RAM for the database. The users directly can see by the response time of the standard input windows if data is loaded from the disks or if it is already in the main memory: if it is in memory the problematic queries take 0.5 to 3 seconds, if it must be loaded it can take also more than 60 seconds if there are other users requiring data from disk. Unfortunately the Windows 64bit Operating System does seem not to make always the best usage of the additional memory: We see many page faults in the processes. But nevertheless I would say: after having a multiprocessor CPU the most important part is the quantity of main memory.

Arne Ortlinghaus
ACS Data Systems

"Pat" <> schrieb im Newsbeitrag
> On May 8, 9:00 pm, "Ana C. Dent" <> wrote:
>> Pat <> wrote in news:12a7f1d9-6dce-4ba5-9d41-
>> When your only tool is a hammer, all problems are viewed as nails.
>> > The classic solution to this is:
>> > add more memory
>> What you are attempting to do is covert Physical I/O to Logical I/O.
>> A smarter solution is to add an index to reduce I/O by orders of
>> magnitude.
> The problem here isn't excessive table scans or an absence of indexes.
> The working set of indexes simply don't fit in cache all that well.
> I've got mutltiple indexes > 1 G in size and a half dozen or so >
> 500M.
> So, while I appreciate the tutorial on the importance of indexes as a
> component to an efficient data retreival strategy, I find it a bit odd
> that you're acting as though cache memory isn't an analagous
> component.
> This is the database back end for an enterprise application, it's not
> a data warehouse application. It tends to aggressively chew over the
> same working set (the aforementioned 10-12G of memory) querying it in
> all sorts of unpredictable, end-user defined, ways. If I knew a set of
> additional indexes I could add that would reduce my working set, I'd
> have already added them. At this point, the only solution I can see
> here is to bump up the SGA so that my (existing) index and data blocks
> fit in memory.
Received on Fri May 09 2008 - 08:05:42 CDT

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