Re: max_connections, solaris semaphores and initdb

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