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Re: SGA size.

From: Matthias Hoys <idmwarpzone_NOSPAM__at_yahoo.com>
Date: Sat, 20 Aug 2005 12:14:16 +0200
Message-ID: <43070279$0$12049$ba620e4c@news.skynet.be>

"TB" <chessgame_at_gmail.com> wrote in message news:1124487289.058599.307530_at_f14g2000cwb.googlegroups.com...
> Hopefully a simple question. I have Oracle 8.1.7 installed on my IBM
> AIX 5.2 server. The server only has 1 GB of RAM and a 2G paging space
> (I'm thinking that is not enough memory). Anyway, I was wondering
> about the size of the SGA. On this one server I have a test database
> and the production database. If I log into either database and do a
> sga show it comes back with:
> SQL> show sga
>
> Total System Global Area 366981012 bytes
> Fixed Size 73620 bytes
> Variable Size 324890624 bytes
> Database Buffers 40960000 bytes
> Redo Buffers 1056768 bytes
>
>
> Are there seperate SGAs for test and prod, or is the SGA for all of
> Oracle and no matter how many data bases you are running, the SGA is
> shared by all?
>
> I hope I'm making at least some sense, I'm not a DBA so forgive me if
> this is a stupid question.
>
> Thanks.
>
> T.
>

Each db has the same init.ora parameters ? Then you have 2*366MB of SGA = 732MB, which can be just enough for a system with only 1GB of RAM. You will also need extra memory for operating system filesystem caching and sorting operations (depending on size of sort_area_size).

You can easily check if you have enough free memory with the command : svmon -G
See the number of "free" pages and multiply by 4. Now you have the amount of free unused memory in KB (each page is 4KB). Swapping can be detected with the vmstat command. See your AIX documentation (or man pages) for more info.

HTH
Matthias Hoys Received on Sat Aug 20 2005 - 05:14:16 CDT

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