Tom Lane wrote:

Doug Y <[EMAIL PROTECTED]> writes:

I've seen a couple references to using ipcs to help properly size shared_buffers.

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."

I've seen references in the admin

I tried all of the dash commands in the ipcs man page, and the only one that might give a clue is ipcs -t which shows the time the semaphores were last used. If you look at the example I give below, it appears as if I'm only using 4 of the 17 semaphores (PG was started on Oct 8).

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). 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.)

                        regards, tom lane

I'm not saying you're wrong, because I don't know how the nitty gritty stuff works, I'm just trying to find something to work with, since presently there isn't anything other than anecdotal evidence. From what I've inferred, there seems to be some circumstantial evidence supporting my theory.


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