Write short notes on the following: Distributed Database

A distributed database is one that can be dispersed or replicated among different points in a network. A distributed database is a database in which storage devices are not all attached to a common processing unit such as the CPU, controlled by a distributed database management system (together sometimes called a distributed database system). It may be stored in multiple computers, located in the same physical location; or may be dispersed over a network of interconnected computers. Unlike parallel systems, in which the processors are tightly coupled and constitute a single database system, a distributed database system consists of loosely coupled sites that share no physical components. The concept of distributed database system was built with a goal to improve reliability, availability and performance.