A distributed database (DDB) is an integrated collection of databases that is physically distributed across sites in a computer network. A distributed database management system (DDBMS) is the software system that manages a distributed database such that the distribution aspects are transparent to the users. To form a distributed database system (DDBS), the files must be structured, logically interrelated, and physically distributed across multiple sites. In addition, there must be a common interface to access the distributed data.
There are many reasons that motivated DDBS. First, distributed databases reflect organizational structure. In many organizations, the data are naturally distributed across departments/branches where each department/branch maintains its own local data. Moreover, it is not always possible to.
