Postgres Server collapse

Hello.

I have a postsgresql database with max 500 connections. All development is in Java (View, Model, controller model). The problem is when I have high traffic (about 10 AM) when the database server collapse. The server turn too slow as It haven´t memory and the swap memory increase too much. I must kill all postgres connections and restart postmaster service.

I have only one connection by web session. It is good or bad?
I have already increased the number of connections to 800 in the postgres and sysctl configuration file.

My server is linux Red Hat and Postgres database V8

Which can be the problem?.

Carlos