Re: Comparing Top 5 Timed Events and Cache Advisory

From: Noons <>
Date: Thu, 16 Jun 2011 17:18:02 -0700 (PDT)
Message-ID: <>

On Jun 16, 11:38 am, vsevolod afanassiev <> wrote:

> This database is running batch processing. We are trying to justify
> purchasing more memory.
> The question is: how much improvement in batch run time we'll get if
> we double memory size? 25%? 50%?

I won't repeat the good advice already given. Just one addition: note that the total batch run time is the sum of *all* I/O wait time *plus* all CPU used to process the data that has been brought into memory.
I cannot see an indication of how much CPU versus how much I/O time is being spent in the batch run.

But I can guarantee you that if CPU is, say, 70% and I/O wait 30%, then the most you can gain by only adding memory is a portion of the I/ O wait, ie, a portion of 30%. It will never exceed that.

However, if you look at the SQL with the intention of reducing how much I/O you have to do to process all data - say, by reducing use of intermediate tables - then you will have an immediate gain that reflects across the board: CPU + I/O.

Worth a shot? In my book: yes. Received on Thu Jun 16 2011 - 19:18:02 CDT

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