Doug Y <[EMAIL PROTECTED]> writes:
> Tom Lane wrote:
>> I have not seen any such claim, and I do not see any way offhand that
>> ipcs could help.
> Directly from:
> "As a rule of thumb, observe shared memory usage of PostgreSQL with 
> tools like ipcs and determine the setting."

[ shrug ... ]  So ask elein why she thinks that will help.

>> This might tell you something about how many concurrent backends you've
>> used, but nothing about how many shared buffers you need.
> Thats strange, I know I've had more than 4 concurrent connections on 
> that box... (I just checked and there were at least a dozen).

There is more than one per-backend semaphore per semaphore set, 16 per
set if memory serves; so the ipcs evidence points to a maximum of
between 49 and 64 concurrently active backends.  It's not telling you a
darn thing about appropriate shared_buffers settings, however.

> A mirror DB with the same config also has the same basic output from
> ipcs, except that it has times for 11 of the 17 arrays slots and most
> of them are the time when we do our backup dump (which makes sense
> that it would require more memory at that time.)

That doesn't follow either.  I think you may have some bottleneck that
causes client requests to pile up during a backup dump.

                        regards, tom lane

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