WebSphere Application Server V7.0: Concepts ... - IBM Redbooks

When using a service such as those provided by the IBM Test Center, you are
presented with large amounts of supporting documentation and evidence to
support the results of the tests. You can use this data to adjust your current
environment.
4.5 Performance tuning
Performance is one of the most important non-functional requirements for any
WebSphere environment. Application performance must be tracked continuously
during your project.
When your project is finished and you switch your environment into production,
you need to be confident that the environment can handle the user load.
Performance problems are by far the most user-visible problem that you can
have. Most users are willing to accept small functional problems when a system
is rolled out, but performance problems are unacceptable to most users and
affect everyone working on the system. Make sure to perform load tests that
represent a realistic user load against your system.
4.5.1 Application design issues
Many performance problems cannot be fixed by using more hardware or
changing WebSphere parameters. As such, you really have to make
performance testing and tuning part of your development process and release
cycles to avoid problems later on. Performance testing and tuning must be
considered in the project schedule.
Note: It is suggested when developing applications to use application profiling
techniques. This allows the development team to identify bottlenecks in the
applications and hot spots where a lot of CPU resources are consumed.
Usually, many hot spots can be removed with little effort.
It takes much more effort and money to correct issues after they occurred in
production than to fix them up front. If performance testing is part of your
development cycle, you are able to correct issues with your application design
much earlier, resulting in fewer issues when using your application on the
production environment.
108 WebSphere Application Server V7.0: Concepts, Planning, and Design