Re: shmmni kernel parameter

On Mon, 24 Aug 1998 17:37:02 GMT, cdoganay_at_my-dejanews.com wrote:

>Hi, I have 2 equivalent database. I have a big performance problem with one of
>them. I wrote an insert PL/SQL script. While it takes 5 seconds to complete on
>the first one, it takes 25 seconds on the other. THE only difference seems
>that shmmni kernel parameter on HP-UX. One has 200 (Faster) and the other is
>3200. Could it be the reason for performance reason?
>
>Any help will be appreciated.
>
>Cemal
>
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Cemal,

Are these machines a) the same confuguration, b) have the same load, c) the same Oracle setup, and d) when was the database last reorganised?

The max number of shared memory identifiers defines the size of the table that manages the memory segments. This is very little overhead to the system.

The only time where shmmni may affect performance is if you run out of them, so I don't think this is your problem! In my experience, as long as the kernel is tuned to provide adequate support for Oracle, then the thing that makes the most difference to performance is the amount of ( relevant part of ) the database that is in memoy when the query is run. Things that affect this are the size of the SGA, and the last time that the data was used. The the only kernel parameter that can affect the size of the SGA is maxdsiz - the maximum size of a data segment, and shmemsiz ( I'm sure I spelled that one wrong! ), which is the maximum size of a shared memory segment. Your SGA needs to be in one piece and contiguous.

If you can post a bit more info, then maybe we can help a bit more!

Cheers,

Steve Received on Tue Aug 25 1998 - 13:08:16 CDT