This book is meant for a wide range of readers, especially college and university students wishing to learn basic as well as advanced processes and techniques of distributed database system. It is intended for those who are professionally interested in having an up-to date view of distributed data processing, including, for example, students and teachers of course in computer science, researchers, system managers, application designers, analysts and programmers. A distributed database system is , in brief an integrated database which is built on top of a computer network rather than on a single computer. The data which constitute the database are stored at the different sites of the computer network. And the application programs which are run by the computers access data at different sites. Modern aspects of distributed database systems have been introduced from the first principles and discussed in an easy manner, so that a beginner can grasp the concepts of disturbed database, its design and architecture level, distributed query processing and optimization, distributed transaction management, distributed concurrency control and reliability, distributed deadlock management, distributed recovery and security management, etc. Each chapter contains solved example problems and exercise problems.