Abstract: The dream of computing power as readily available as the electricity in a wall socket is coming closer to reality with the arrival of grid and cloud computing. At the same time, databases grow to sizes beyond what can be efficiently managed by single server systems. There is a need for efficient distributed database management systems (DBMSs). Current distributed DBMSs are not built to scale to more than tens or hundreds of sites (i.e., nodes or computers). Users of grid and cloud computing expect not only almost infinite scalability, i.e., at least to thousands of sites, but also that the scale is adapted automatically to meet the demand, whether it increases or decreases. This is a challenge to current distributed DBMSs. The purpose of this paper is to present an introduction to Distributed Databases which are becoming very popular now a days. Today’s business environment has an increasing need for distributed database and Client/server applications as the desire for reliable, scalable and accessible information is Steadily rising. Distributed database systems provide an improvement on communication and data processing due to its data distribution throughout different network sites.
Keywords: Distributed databases fundamentals, current research: query optimization, distribution optimization, fragmentation optimization.
I . Introduction
In today’s world of universal dependence on information systems, all sorts of people need access to companies’ databases. In addition to a company’s own employees, these include the company’s customers, potential customers, suppliers, and vendors of all types. It is possible for a company to have all of its databases concentrated at one mainframe computer site with worldwide access to this site provided by telecommunications networks, including the Internet. Although the management of such a centralized system and its databases can be controlled in a well-contained manner and this can be advantageous, it poses some problems as well. For example, if the single site goes down, then everyone is blocked from accessing the databases until the site comes back up again. Also the communications costs from the many far PCs and terminals to the central site can be expensive. One solution to such problems, and an alternative design to the centralized database concept, is known as distributed database. In short a distributed database is a collection of databases that can be stored at Different computer network sites. Each database may involve different database management systems and different architectures that distribute the execution of transactions. The objective of a distributed database management system (DDBMS) is to control the management of a distributed database (DDB) in such a way that it appears to the user as a centralized database.
II. DISTRIBUTED DATABASES
A distributed database management system (DDBMS) is the software that manages the DDB, and provides an access mechanism that makes this distribution transparent to the user. Distributed database system (DDBS) is the integration of DDB and DDBMS. This integration is achieved through the merging the database and networking technologies together. Or it can be described as, a system that runs on a collection of machines that do not have shared memory, yet looks to the user like a single machine. A distributed database (DDB) is a collection of multiple, logically interrelated databases distributed over a computer network. A distributed database management system (distributed DBMS) is the software system that permits the management of the distributed. A distributed database (DDB) is a collection of multiple, logically interrelated databases distributed over a computer network. The term distributed database system (DDBS) is typically used to refer to the combination of DDB and the...