Web Page is showing not available though the execution is still in progress

I've a web project using Java and JSP, which gathers informations writes in an excel sheet. When the data count is much less, the web page is working fine and redirecting exactly where it is supposed to do but when the data count is high, the web page is showing that the "web page is not available" though the execution is still going on in background. I'm running my code in eclipse and I'm using tomcat 6. Any kind of help is appreciated. Thanks!