Need of Distributed Database - DDBMS


Need of Distributed Database

The distributed databases are needed because of the following reasons:

Organisation and Economic Reasons: With the recent development ,of computer technology, the economy of scale motivation for having largege, centralised computer centre is becoming questionable.

Interconnection of Existing Database:  Distributed  database are the natural solution when  several  database already exist in an organisation and the necessity of performing  global, application arises.

In this case, the distributed database is created bottom-up from the pre-existing local database. This process may require a certain degree of local restructuring.

Incremental Growth: Distributed database easily used in new  branches and new warehouse.

With a centralised approach, either the initial dimensions of the system take care of future expansion, which is difficult foresee and expensive to implement, or the growth has a major impact not only on the new application but also on the existing ones.

Reduced Communication Overhead: In a geographically distributed database, we use local application, which reduces communication overhead. Therefore, the maximisation of the locality of applications is one of the primary objectives in distributive database design.

Performance: Due to high degree of parallelism it gives autonomous result. This consideration can be applied to any multiprocessor system, and not only to distribute databases but also so allows parallelism, but is not considered a distributed database. However, distributed database have the advantage that the decomposition of data reflects application criteria which depends on maximising the application locality, in this way the mutual interference between different processors is minimised. The load is shared between the different processors and critical bottlenecks such as the communication network itself services of the whole or common system, are avoided.

Reliability and Availability: The distributed database approach especially with redundant data can be used also in order to obtain higher reliability and availability.

However, obtaining this goal is not straightforward and requires the use of technique, which is still not completely understood. The autonomous processing capability of different site does not by itself guarantee a higher overall reliability of the system, but it ensures a graceful degradation property.