Performance Problems

Abstract

Too often, tuning begins when an application’s development is already finished. This is unfortunate because it implies that performance is not as important as other crucial requirements of the application. Performance is not merely optional, though; it is a key property of an application. Not only does poor performance jeopardize the acceptance of an application, it usually leads to a lower return on investment because of lower productivity. In fact, as shown in several IBM studies from the early 1980s, there is a close relationship between performance and user productivity. The studies showed a one-to-one decrease in user think time and error rates as system transaction rates increased. This was attributed to a user’s loss of attention because of longer wait times. In addition, poorly performing applications lead to higher costs for software, hardware, and maintenance. For these reasons, this chapter discusses why it is important to plan performance and how to know when an application is experiencing performance problems. Then the chapter covers how to approach performance problems on a running system.