Configuration Parameters

I am setting up a web-based app on Apache, JServ and PostgreSQL 7.0 running
on freeBSD. Occasionally I get a "Too many clients" exception, which I can
work around by rebooting Apache. I understand this may be a configuration
problem, but I am not sure how to proceed.

If I expect about 50 concurrent full-time users, what are appropriate -N
and -B values for the postmaster? What would be appropriate values for
SHMMAX, SEMMNS, SEMMNI, NPROC, MAXUPRC, NFILE and NINODE? Are there any
other configuration parameters that I need to worry about?

What is the mechanism for shutting down postmaster instances? Should my
Java servlets do this explicitly?

Thanks in advance,
Richard Ehrlich