IBM® WebSphere® Application Server supports an ever-growing range of applications, each with their own unique set of features, requirements, and services. Just as no two applications will use an application server in exactly the same way, no single set of tuning parameters will likely provide the best performance for any two different applications. Most applications will generally realize some performance improvement from tuning in three core areas: the JVM, thread pools, and connection pools. This article uses the Apache DayTrader Peformance Benchmark Sample application to demonstrate what you can tune and how to go about tuning it, depending on the major server components and resources that your application uses.

http://www.ibm.com/developerworks/websphere/techjournal/0909_blythe/0909_blythe.html