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RE: Adding CPU to a unix box--added capacity.

From: Herring Dave - dherri <>
Date: Sat, 3 Nov 2007 08:55:31 -0500
Message-ID: <>

The best I can offer is my opinion and understanding of Craig's book. Yes, I felt it was an excellent book for the subject matter and has given us hope in finding ways to forecast anything related to Oracle performance. The key (from my understanding) is trying to somehow determine how existing processes relate to resource usage. For example, you don't just have 50% CPU usage. You have x number of groups or applications performing different functions which together consume 50% of CPU resources. Try to break that up to show application A or group of users A use x% of CPU resources, application B uses y% of CPU resources, etc. From there you can (with a variety of methods outlined in Craig's book) try to forecast that if application A or B grows by a given amount, what would the impact be and how you could best address it.

Again, all based on my understanding of the book's content. HTH.


David C. Herring, DBA  |   A c x i o m  Delivery Center Organization 630-944-4762 office | 630-430-5988 wireless | 630-944-4989 fax

From: [] On Behalf Of Zhu,Chao Sent: Friday, November 02, 2007 9:32 AM
To: oracle-l
Subject: Adding CPU to a unix box--added capacity.

    Does anyone have experience on adding new CPU to a existing box, like upgrade from 8CPU to 16 CPU for example.
    I am curious about two things;

1. How many CPU usage% drop do we expect? Like previously it is running at 50% CPU usage,  typically will it drop to 25%? or something like 30%? To ask the same question from another view, is , how much capacity we add to the box? 16CPU box = 1.X(?) of a 8CPU box. Assuming same archtecture/OS. (same cpu count server in different architecture may have different processing power?)
  Would be nice if you can share with your experience (like on solaris/aix/hp etc). That's kind of typical server scalability.

2.   Can we say,  CPU_USED_BY_THIS_SESSION (stat in oracle) ~~ Unix_CPU_COUNT * USER_MODE_CPU% (vmstat usr column)? I did couple of compare in my database, they look pretty close.

    Does anyone ever thinking about have such a formular: it could be very fun.
CPU_USED_BY_THIS_SESSION = X*logical_reads + Y*physical_reads + Z*sorts + A * executions + B * redo_size + C * Latch_Spins+ .......?

by the way, anyone like the book"forecasting oracle performance"?

Zhu Chao
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Received on Sat Nov 03 2007 - 08:55:31 CDT

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