This book is written for a broad audience, but it is mainly targeted at college and university students who want to learn both the fundamental concepts and sophisticated methods of distributed database systems. It is aimed at those who want a current understanding of distributed data processing for professional purposes, such as, for instance, students. in addition to researchers, system managers, application designers, analyzers, and programmers, of course, as well as teachers of computer science. An integrated database that is created on top of a computer network rather than on a single computer is, in essence, a distributed database system. The application programmes that are performed by the computers access data at various sites, while the data that make up the database are stored at various locations across the computer network. 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 Distributed Databases, 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.