a few questions

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 the 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 the 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 running.
my question is that can u decrease this timeout, right now i think it takes 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 stopped.

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 postmaster 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 database 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,
--
Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/

On Thu, Dec 29, 2005 at 03:40:11PM +0530, surabhi.ahuja wrote:

pidof of doesnt work ?

Given the number of processes is going to be at least 3+number of
connections, how is pidof going to know which one you mean? Answer: it
doesn't, so you end up killing a random one.

which startup script are u reffering to?

In recent releases they're under contrib/start-scripts but they've been
there for a while. Since you didn't say which version, I can't help you
more than that.

Have a nice day,
--
Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/

On Fri, Dec 30, 2005 at 06:21:28PM +0530, surabhi.ahuja wrote:

I am working with PostgerSQL 8.0.0.
where can i find the startup scripts for the same.

Well, it's been in contrib/strat-scripts since 8.0.0 so you should find
it there.

One more thing,
I could not understand this:
number of processes is going to be at least 3+number of connections

do u mean that for each connection there is a "postmaster" process? and what are those 3 processes?
actually the ppl who use the application often use kill -9 postmaster. in such a case the pid file still remains.

One postmaster, 2 for the stats collector and possibly 1 for the
autovacuum daemon. Plus one for each connection to the database.

People shouldn't use kill -9 on the postmaster, they should use the
normal signals, or just "pg_ctl stop". Or if you use a startup script,
/etc/init.d/postgresql start/stop.

Have a nice day,
--
Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/