The Evolution of Distributed Database Management Systems
A distributed database management system (DDBMS) governs the storage and processing of logically related data over interconnected computer systems in which both data and processing are distributed among several sites.
The use of a centralized database required that corporate data be stored in a single central site, usually a mainframe computer. Data access was provided through dumb terminals. The centralized approach worked well to fill the structured information needs of corporations, but it fell short when quickly moving events required faster response times and equally quick access to information. The slow progression from information request to approval to specialist to user simply did not serve decision makers well in a dynamic environment.
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The factors influenced the evolution of the DDBMS:
The different factors influenced the evolution of the DDBMS are as follows.
• The growing acceptance of the Internet as the platform for data access and distribution which leads to maintain the repository for distributed data.
• The wireless revolution. The widespread use of wireless digital devices, such as smart phones like the iPhone and BlackBerry and personal digital assistants (PDAs), has created high demand for data access. Such devices access data from geographically dispersed locations and require varied data exchanges in multiple formats (data, voice, video, music, pictures, etc.) Although distributed data access does not necessarily imply distributed databases, performance and failure tolerance requirements often make use of data replication techniques similar to the ones found in distributed databases.
• The accelerated growth of companies providing “application as a service” type of services. This new type of service provides remote application services to companies wanting to outsource their application development, maintenance, and operations. The company data is generally stored on central servers and is not necessarily distributed. Just as with wireless data access, this type of service may not require fully distributed data functionality; however, other factors such as performance and failure tolerance often require the use of data replication techniques similar to the ones found in distributed databases.
• The increased focus on data analysis that led to data mining and data warehousing. Although a data warehouse is not usually a distributed database, it does rely on techniques such as data replication and distributed queries that facilitate data extraction and integration.
The Problems with the Centralized Database Management System:
• Performance degradation because of a growing number of remote locations over greater distances.
• High costs associated with maintaining and operating large central (mainframe) database systems.
• Reliability problems created by dependence on a central site (single point of failure syndrome) and the need for data replication.
• Scalability problems associated with the physical limits imposed by a single location (power, temperature conditioning, and power consumption.)
• Organizational rigidity imposed by the database might not support the flexibility and agility required by modern global organizations.
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