The purpose of this document is to explain how to go about performing scalability testing, performance testing, and optimization, in a typical Java 2 Enterprise Edition (J2EE) environment.
Response Time the time it takes between initial request and complete download of response (rendering of entire web page).
Load a measurement of the usage of the system. A server is said to experience high load when its supported application is being heavily trafficked.
Scalability - A scalable application will has a response time that increases linearly as load increases. Such an application, will be able to process more and more volume by adding more hardware resources in a linear (not exponential) fashion.
Automation testing tools Tools (Silk from Segue Software, WebLoad, etc) used to simulate a user by requesting pages or going through pre-programmed workflow on your site.
Load testing tools Most automation testing tools can also be used as load testing software, like WebLoad. These tools will simulate any number of users using your site and provide you with important data like average response times.
Profiler. A profiler is a program that examines your application as it runs. It provides you with useful run time information such as time spent in particular code blocks, memory / heap