Обсуждение: postgresql.conf shared buffers

Hi all,

- What does the shared_buffers setting do ?
- Does it mean that that the postgres cannot access most of the physical RAM but limited to the memory setting
(shared_buffers)specified ? 
- How do i relate and set max_connections and shared_buffers?
- Is there a thumb rule to determine shared_buffers from max connections ?
- I see , by default max_connections set to 100 and shared_buffers to 1000 - does 1000 mean 1000 bytes or KB ?
- Also postgres will not start if the shared_buffers value exceeds the kernel setting of SHMMAX. do i need to recompile
thekernel to increase this value ? or is there any workaround ?  

tia,
regards,
KM

Please take a look at
http://www.varlena.com/GeneralBits/Tidbits/annotated_conf_e.html first.

In a nutshell, set shared_buffers to between 10% and 25% of your memory
if it's a server. And increase estimated_cache_size to something close
to how much memory you have.

On Tue, Oct 03, 2006 at 07:50:42PM +0530, km wrote:
> Hi all,
>
> - What does the shared_buffers setting do ?
> - Does it mean that that the postgres cannot access most of the physical RAM but limited to the memory setting
(shared_buffers)specified ? 
> - How do i relate and set max_connections and shared_buffers?
> - Is there a thumb rule to determine shared_buffers from max connections ?
> - I see , by default max_connections set to 100 and shared_buffers to 1000 - does 1000 mean 1000 bytes or KB ?
> - Also postgres will not start if the shared_buffers value exceeds the kernel setting of SHMMAX. do i need to
recompilethe kernel to increase this value ? or is there any workaround ?  
>
> tia,
> regards,
> KM
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: don't forget to increase your free space map settings
>

--
Jim Nasby                                            jim@nasby.net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)

On Oct 11, 2006, at 03:34 , Jim C. Nasby wrote:

> And increase estimated_cache_size to something close
> to how much memory you have.

That would be "effective_cache_size".

Alexander.

Jim, list,

from your link:

I quote:

"""As a rule of thumb, observe shared memory usage of PostgreSQL with tools like ipcs and determine the setting. Remember that this is only half the story. You also need to set effective_cache_size so that postgreSQL will use available memory optimally.
"""

and add the question (not necessarily to you):

-what is the best way to obsere shared memory usage on win32?

- which memory-size should be taken for "effective_cache_size" on windows servers with multpile purposes (i.e.: more then PostgreSQL running on them)
 Available are (propable ones): physical memory, system cache, available memory (depends on system load)

Harald



--
GHUM Harald Massa
persuadere et programmare
Harald Armin Massa
Reinsburgstraße 202b
70197 Stuttgart
0173/9409607
-
Python: the only language with more web frameworks than keywords.