PostgreSQL Shared Memory and Semaphors

From: "pobox(at)verysmall(dot)org" <pobox(at)verysmall(dot)org>
To: pgsql-general(at)postgresql(dot)org
Subject: PostgreSQL Shared Memory and Semaphors
Date: 2006-10-13 20:12:21
Message-ID: 452FF325.9010905@verysmall.org
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Hello,

I want to increase the max_connections of PostgreSQL from around 40 to
around 100. For this I need to change the Shared Memory and Semaphores
settings.

I followed this link -

http://www.postgresql.org/docs/8.1/interactive/kernel-resources.html#SYSVIPC

and used the proposed values in a test installation FreeBSD 5.5,
PostgreSQL 8.x, with 96 MB RAM (a VMware guest) -

I added -

kern.ipc.shmall=32768
kern.ipc.shmmax=134217728
kern.ipc.semmap=256
to /etc/sysctl.conf

kern.ipc.semmni=256
kern.ipc.semmns=512
kern.ipc.semmnu=256
to /boot/loader.conf

And I changed max_connections = 40 to 100 in postgresql.conf.

Rebooted and all works OK.

Now I want to do the same on a production machine FreeBSD 5.4,
PostgreSQL 8.x, with 2 GB RAM.

Are there any dangers I should have in mind?

Thank you,
Iv

PS I know that the values can be compiled into the kernel, but I am not
that good yet.

PPS I posted this first to 'FreeBSD questions' but there was no response
there.

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