Re: Determining Memory Allocations - Dedicated/Shared Server

From: Mark D Powell <>
Date: Sat, 26 Jan 2008 15:07:50 -0800 (PST)
Message-ID: <>

On Jan 24, 6:50 pm, "Dereck L. Dietz" <> wrote:
> I've found "formulas" for determining the SGA/PGA sizing for a dedicated
> server.
> Using a formula from  the Burleson Consulting web site I was able to come up
> with these figures:
>                                                           --  8 GB --   --  
> 16 GB --    -- 32 GB --
> Total RAM on Windows Server         8,191.0 MB 16,384.0 MB 32,767.0 MB
>  Less:
>  Total PGA regions for 100 users        3,980.0 MB  3,980.0 MB  3,980.0 MB
>  RAM reserved for Windows (20%)   1,638.2 MB  3,276.8 MB  6,553.4 MB
>  RAM for SGA & Buffers                   2,572.8 MB  9,127.2 MB 22,233.6 MB
> What I've been trying to find out is how would I determine the memory
> allocations if both dedicated and shared connections would be in use?  Is
> the memory allocated for a shared server configuration, a dedicated server
> configuration or is there a "hybrid" server configuration that's used?

I would like to point out the the total necessary memory requirement for running Oracle using dedicated sessions and shared server connections is pretty much equal. In the case of shared server you move memory from the PGA to the SGA to support the concurrent user load. What you mostly save is the OS process overhead, that is, you reduce the number of OS processes necessary. This will not save you a lot of memory compared to using dedicated sessions. It will however allow you to run if you were nearing your total process limit which was much more limited just a few years ago.

In Tom Kyte's book on Oracle Architecture you can find a demonstration showing nearly equal memory requirements for the same load under both connection process management methods.

HTH -- Mark D Powell -- Received on Sat Jan 26 2008 - 17:07:50 CST

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