Compiling JSPs is a resource-intensive and relatively time-consuming process. By default, the Web Server periodically checks to see if your JSPs have been modified and dynamically reloads them; this allows you to deploy modifications without restarting the server. The reload-interval property of the jsp-config element in sun-web.xml controls how often the server checks JSPs for modifications. However, there is a small performance penalty for that checking.
When the server detects a change in a .jsp file, only that JSP is recompiled and reloaded; the entire web application is not reloaded. If your JSPs do not change, you can improve performance by precompiling your JSPs before deploying them onto your server. For more information about jsp-config and about precompiling JSPs for Sun Java System Web Server, see the Sun Java System Web Server 6.1 SP9 Programmer’s Guide to Web Applications. Also see the following section, Configuring Class Reloading.