Date: Thu, 29 Dec 2005 10:54:05 +0100
From: Martijn van Oosterhout <kleptog@svana.org>
To: "surabhi.ahuja" <surabhi.ahuja@iiitb.ac.in>
Cc: pgsql-general@postgresql.org
Subject: Re: a few questions
Message-ID: <20051229095359.GB17809@svana.org>
Reply-To: Martijn van Oosterhout <kleptog@svana.org>
Mail-Followup-To: "surabhi.ahuja" <surabhi.ahuja@iiitb.ac.in>,
	pgsql-general@postgresql.org
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On Thu, Dec 29, 2005 at 03:09:52PM +0530, surabhi.ahuja wrote:
>  I have a few questions:
> 1. what is pg_xlog
> someone told me that i can move pg_xlog to a different parttion in order =
to boost the performance? Does it work and how

Yes, it works. How? By moving the directory (while the postmaster is
not running) and creating a symlink in the right place.

> 2. there is a parameter in postgresql.conf called max_connections. which =
is 100 be default. i want o decrease it to 20.
> by doing this how much can i increase the value of shared buffers?
> by default it is 1000, how much can i increase to in order to boost up th=
e performance

They have nothing to do with eachother. Depending on how much memory
you have, the shared_buffers could be increased by a factor of 10. Max
connections won't change anything there.

> 3. What other things can i do to boost up the performance assuming that t=
he stored procedures are well optimized.

Google the web, or try the pgsql-performence mailing list.

> 4. I recently tried to start postmaster. But it simply timed out. i tried=
 to find out if there is any postmaster process running, but it was not run=
ning.
> my question is that can u decrease this timeout, right now i think it tak=
es some 1 or 2 minutes...

Look in the logs for an error message.

> 5. i have also seen multiple instances of postmaster.
> in my script ot start postmaster i first check if it is running by doing =
pidof, and only if it is nor running i start it
> still have seen multiple instances.
> how did that happen? also if i stop postmaster, only one instance is stop=
ped.

Each connection appears as a new process, so pidof wont't work. You
need to use the pidfile the postmaster creates. Why arn't you using one
of the startup scripts provided?

> is there any command to stop all instances of postmaster

Are you sure you have more than one?

> 6. what does ipcclean do? how do i know what shared memory was used by po=
stmaster so that i can clear it, before starting postmaster

PostgreSQL takes care of it's own ipc memory, you should never need to
use ipcclean ever.

> 7. some times if i do a dropdb abc(assuming abc is a database)
> it displays a message can not remove directory 12345, although the databa=
se is dropped, what shuld be done in such a case?

Please provide the exact error message. Oh, and while you're at it,
what platform and what version of postgres. Without that info it's
impossible to give any real help,

Have a nice day,
--=20
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.

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