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Re: How many private memory does one single oracle server process allocate?

From: joel garry <joel-garry_at_home.com>
Date: 25 Oct 2006 13:40:56 -0700
Message-ID: <1161808856.757582.120410@e3g2000cwe.googlegroups.com>

lsllcm wrote:
> Hi Joel,
>
> I have read an article, 259983.1 "Memory Consumption on AIX",there is
> one bug about memory.
>
> One connect allocate about 5M and the connection do nothing, so I want
> to check how can we identify this kind of issue.
>
> I don't know whether we can use v$sesstat, so I post this message.
>
> Thanks

Ah, interesting article, I think I see you asking if there is some way to predict how much memory each session will use based on analysing compilation of the oracle executable.

Perhaps there is, but I haven't really gone through that exercise. I haven't had any reason to, in my experience it is more useful to measure what is actually happening with a user load. The amount of memory actually used in a session is impacted by many more things than what is compiled into the executable. The article you've cited simply shows that some configurations can use much more memory per session initially. From my viewpoint, that is mostly irrrelevant, as I would look at the specific and overall sessions memory usage for whatever configuration I have. Even for capacity planning, you can only really be accurate with empirical measurements. Some queries will use more memory than each session has available, so Oracle uses temp files for those things. You can configure Oracle to tell sessions to max at a certain amount of memory, details vary by version.

Predicting memory usage becomes even more convoluted in shared server configurations.

See your DBA about accessing v$ tables.

Also, once you start getting into details specific to an OS, especially idiosyncratic AIX, it varies as to how much you can apply that to something with completely different code like linux.

Just because you made me curious, I did a size -f on two different hp-ux machines with the same oracle patch level but slightly different OS patch levels, and the .data sections were .5K different. It's that kind of thing that makes me advise people to use the oracle installer rather than copying over installations, it's tough to keep any two machines exactly the same. But I apparently have a minority opinion about that.

jg

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Received on Wed Oct 25 2006 - 15:40:56 CDT

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