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Re: max_connections, solaris semaphores and initdb

From: Isaac Vetter <ivetter(at)math(dot)purdue(dot)edu>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-novice(at)postgresql(dot)org
Subject: Re: max_connections, solaris semaphores and initdb
Date: 2008-01-11 19:17:41
Message-ID: 4787C0D5.4080203@math.purdue.edu (view raw or flat)
Thread:
Lists: pgsql-novice
Tom Lane wrote:
> Isaac Vetter <ivetter(at)math(dot)purdue(dot)edu> writes:
>> I'm running postgresql 7.4 on Solaris 9 and want to increase the value 
>> of postgresql.conf's max_connections for an existing, running install. 
>> I've edited /etc/system to what I think are more appropriate, but 
>> definitely higher, values. Then I changed the value of max_connections 
>> to 768; however, by watching the pg_stat_activity view and the 
>> serverlog, connections are rejected when the number of connections 
>> approaches 200 (with the infamous: "FATAL:  connection limit exceeded 
>> for non-superusers" error).

Hi Tom;

> Um, did you restart the postmaster?  This is a
> can't-change-after-startup parameter.

Yes. I've restarted. Even rebooted to have the /etc/system changes take 
effect. My concern is that there's a value somewhere that quietly sets 
an upper limit on what max_connections can be, that is determined from 
kernel settings when initdb is run.

This page:
http://www.postgresql.org/docs/7.4/static/runtime-config.html

contains this line describing the max_connections parameter:

"The default is typically 100, but may be less if your kernel settings 
will not support it (as determined during initdb). This parameter can 
only be set at server start. "



0) Is this correct? Does initdb set an unchangeable value that quietly 
limits the high end of max_connections?

1) Is there a way to get postgresql to reset this value, which 
determines the maximum value of max_connections, without dumping, 
re-running initdb and loading? Is there a way to see what this value is?

2) Are there any easy postgresql load testing tools? I ran across Tsung, 
  but haven't had time to compile erlang. What do others do for load 
testing?



Thanks,

Isaac Vetter

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Next:From: Tom LaneDate: 2008-01-11 20:20:11
Subject: Re: max_connections, solaris semaphores and initdb
Previous:From: LWATCDRDate: 2008-01-11 18:58:23
Subject: Re: Connecting to the database server

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