Postgresql shared_buffer and SHMMAX configuration.

Hi,

Recently we upgraded our production server from 7.5GB RAM to 15GB RAM.
    1. To solve performance issue.
    2. Also the number of concurrent users increased from 150 to 300.

Our production server is not dedicated server. We have also

1. Tomcat
2. Apache
3. Cron based scheduled programs
4. Also some thread based programs

running in the same server.

We are trying to configure postgresql parameters according to 15GB RAM.

Linux
---------------
Kernal.SHMMAX
    From - 2147483648
    To   - 19818063053

250kB + 8.2kB * shared_buffers + 14.2kB * max_connections
(250kB + 8.2kB * 2359296kB(2304*1024) + 14.2kB * 500) = 19353577.2 * 1024 =
19818063052.8

postgresql.conf
--------------------
shared_buffers
    From - 1536MB
    To - 2304MB

Since we have other application also running we have taken 15% of the RAM
value for shared_buffers.

max_connection
    From - 500
    To - 500

PGPOOL configuration
---------------------
num_init_children
    From - 150
    To - 420
child_max_connections
    From - 20
    To - 30

We have more than 300 peoples accessing our server concurrently so we need
around 300 connections concurrently.
Is this correct? Will the above configuration improve the performance?

Thanks in advance

Regards
Ezhil