Java HotSpot Virtual Machine

Hi! I have a critical application on my company. This application is made of JSP and Servlets, with Servlets bieng the 80-90% of the site. I had a test the last week with 700 employees. The application went OK the first ten minutes and then stop responding. The Tomcat didn't crash, but the browsers just can't get the pages, they keep "loading". Monitoring the resources, the processor was in less than 2%, memory about 4% and the network in 1%, so I don't know what really happened.

My configuration is a Tomcat 5.5, JDK 1.5 in a foure processor Solaris SPARC with 64 Gb of memory and a 1 Gb network (all the building is at 1 Gb network, not just the server) and in another server, I have a PostgreSQL 8 installation, in a server with almost the same hardware.

What do you think was the problem? Right now I'm trying to figure that out and tune my environment. For the % of the resources, I can see that it wasn't a problem of insufficient resources, but something in the configuration went wrong.

My tomcat didn't had the native library, I've put it right now. What other configuration and tuning can I do? Does Tomcat runs by default with JRE server (HotSpot) or it must be specified? What other tuning can I make on tomcat, something of threads maybe?

I don't have any error on the log files of Tomcat.

And another "adjacent" question... is there a real reason tu limit the Heap Space to 4 Gb? I know that in Solaris you can use that qty, and in other OS you must use less, but why is this, why is the reason behind this?

Thanks a lot for your help in any of my questions.