Computing power performance was important at times when hardware was still expensive, because hardware had to be employed optimally. Later on this criterion was no longer critical, since hardware had become inexpensive. Meanwhile, however, people have realized that performance again plays a significant role, because of the large input of system resources when developing complex applications. This book distinguishes between three levels of performance optimization: system level, application level and business processes. On each level optimizations can be realized and cost-cutting potentials can be identified. The relevant theoretical background and measuring methods as well as solution proposals are presented. An evaluation of network monitors and checklists completes the work.