Evaluation of Distributed Data Base Management Systems and also Explain Advantages & Disadvantages ?

DDBMS governs the storage & processing of logically related data over interconnected computer system in which both data and processing functions are distributed among several sites.

During 1970’s corporations implemented centralized DBMS to meet their structured information needs.

The use of a centralized database required that corporate data be stored in a single central site usually a main frame computer. Data access was provided through dumb terminals.

The last two decades technological check affected database development and design. Those changes were 1. Business operations became decentralized 2. Competition increased at global level 3. Customer demands & market needs favored a decentralized management style 4. Rapid technological change created low cost computer. Multiplication handled portable wireless devices with cellular phone & data services. During recent years the factors are strongly influenced.

The growing acceptance of the internet as the platform for data access & distribution :

WWW is the repository for distributed data.

Wireless revolution : The personal digital assistants (PDAS) like palm & black berry and multipurpose ‘smart phones’ like phone has created high demand for data access. Such devices access data from geographically dispersed locations & require varied data exchanges in multiple formats. The decentralized data base is especially desirable because centralized management is subject to problems such as 1. performance degration 2. High costs associated with maintain & operate large central data base system

Scalability problem :

Physical limits imposed by a single location ( power consumption , temperature conditioning )

The dynamic B/s environment & the centralized data bases short comings spawned a demand for applications based on accessing data from different sources at multiple locations such a multiple source / multiple locations data base environment is best managed by a distributed DBMS

DDBMS advantages and disadvantages :

Advantages disadvantages 1. data are located near the greatest demand site 1. complexity of management and control 2.Faster data access 2. Technology difficulty such as data integrity, transaction, management , concurrency control, security, backup, recovery  & so on. 3. Faster data processing because DDBMS maintain several sites to process the data 3. security :Data is located at different sites & used by different people 4. Growing facilitation : Now site can be added without affecting of the operations on other site 4. lack of standards : there are no standard communication protocols at the data base level 5. improved communication :Local sites are smaller & located closer to customers , local sites provide better communication among departments & customer & staff 5. Increased storage & infra structure requirements : Multiple copies of data are required at different sites, thus requiring additional disk storage space 6. Reduced operating costs 6. Increased training costs 7. User friendly interface 7. costs : DDBMS require duplicated infrastructure to operate ( physical location , environment, s/w , licensing etc., ) 8. processor Independence: The user is able to access any available copy of the data & an end users request is processed by any processor at the data location.