Distributed Database Management Systems

Little bit of History

• Traditional File Processing System: the very first form of business data processing
• Each program contains data description that it manipulates
• Redundancy of data
• Problems in maintenance

File Processing Systems

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Duplication of Data

Vulnerable to Inconsistency

Database Approach: (Also called centralized database) Database is a shared collection of logically related data

Database Approach

• Takes care of all major drawbacks of File System Environment plus more

Distributed Computing System

• A number of autonomous processing elements that are connected through a computer network and that cooperate in performing their assigned tasks
• Distributed System Software enables computers to coordinate and share
• The thing being distributed?

1. Processing logic
2. Functions
3. Data
4. Control; All are relevant and important here

Classifications of DCS

• Degree of Coupling

1. How closely systems are connected
2. May be the measured as ratio of messages interchanged to the local processing
3. Could be Weak (over the network) or Strong (if components are shared)

• Interconnection structure

1. Could be point to point or a common interconnection channel

• Interdependence of Components
• Synchronization
• Factors are not totally independent

Why DCS?

• Suits some of the Organizational Structures; more reliable and responsive
• Nature of some applications
• Technological Push

DCS’s Alerts

• Information Islands and Lack of Standards
• Difficulties in Large Application Design
• Too Many Options Available

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