Enterprise systems supporting business processes in large companies and organizations, are critical for their business survival, and expensive to build and run. This book describes successful approaches to designing, and tuning for performance, large enterprise systems. In contrast to earlier mainframes, the modern distributed systems contain large numbers of components and simple capacity planning methods, applicable to mainframes, cannot be used for design or tuning of complex distributed systems. Methods that have proven to be successful are based on building predictive models that take into account key characteristics of hardware, software, data and communications.