From: Sabrina Lautier (slautier@amadeus.net)
Date: Wed Jan 14 2004 - 14:13:28 EST
Admins,
Thanks a lot to all of you who responded, you've helped me a lot.
After this posting I realized I hadn't said enough in my mail...
The server I'm talking about is a Sun Solaris 8 one with 16GB of memory,
16GB of swap and 8 CPUs.
This a dev. server and not a production one.
Unfortunately it's aimed to both Oracle and developers... this will change
as requested in the Unix team but when ?
Oracle is running on it, but curiously this request doesn't come from our
DBA but from our developers themselves.
In fact the oracle DBs are small and the total SGA for all DBs is 2GB.
The biggest memory segment a DB use is 300MB. So he doesn't need me to
increase this parameter.
A developer team needs to create 1 GB shared memory segment because they
want to put an entire 1GB flat file into memory.
To my opinion they'd rather put this file content in an oracle DB which
will managed better this shared memory but I know that I won't dissuade
them from doing what they want...
At the moment as shmmax is set to 512MB they address two 512MB memory
segments.
I understand that they've better use only one 1GB segment than two 512MB
ones but I'm afraid they lock up all the available memory by running their
application several times on the same machine (that's what usually they
do).
I also do not want that the other teams (which doesn't need such an amount)
start using 1GB memory segments too.
I going to investigate further the shared memory utilization on the machine
with vmstat as you recommend and check how things turns out.
Don't hesitate to tell me if I'm wrong on one or several points.
Again thanks a lot for your precious help.
Sabrina
----- Forwarded by Sabrina Lautier/NCE/AMADEUS on 14/01/2004 20:05 -----
From: Sabrina Lautier <slautier@amadeus.net>@sunmanagers.org on
11/01/2004 02:05
Sent by: sunmanagers-bounces@sunmanagers.org
To: sunmanagers@sunmanagers.org
cc:
Subjec System parameter shmmax
t:
Admins,
Developers here ask me to increase the value of the system parameter shmmax
(maximum amount of memory that can be addressed in a shared memory segment)
to 1GB.
Its actual value is 512MB.
512MB was already a lot for me so 1GB is just so huge !
How does this sound to you ? Is this value big ?
As the server conserved has already poor performances (way too loaded),
I've tried to tell them that they may have serious Pb to keep working on
it...
I'm looking for documentation to be able to give them good explanation.
Can some of you give some interesting links to shared memory related
information or inform me about what you know ?
Thanks for your help.
Sabrina
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