Data management in distributed data bases

The recent advances in large-scale integrated logic and memory technology, coupled with the explosion in size and complexity of the application areas, have led to the design of distributed architectures. Basically, a Distributed Computer ·System (DeS) is considered as an interconnection of digital systems called Processing Elements (PEs), each having certain processing capabilities and communicating with each other. This definition encompasses a wide range of configurations from an uniprocessor system with different functional units to multiplicity of general-purpose computers (e.g. ARPANET). In general, the notion of "distributed systems" varies in character and scope with different people. 30 So far, there is no accepted definition and basis for classifying these systems. In this paper, we limit our discussion to a class of DCSs which have an interconnection . of dedicated/shared, programmable, functional PEs working on a set of jobs which may be related or unrelated. Due to the information explosion and the need for more stringent requirements, the design of efficient coordination schemes for the management of data on a DCS is a very critical problem. Data on a DCS are managed through a data base. A Data Base is a collection of stored operational data used by the application systems of some particular enterprise,6.12 and a Distributed Data Base (DDB) can be thought of as the data stored at different locations of a DCS. It can be considered to exist only when data elements at multiple locations are interrelated and/or there is a need to access data stored at some locations from another location. Due to the ever-increasing demand for on-line processing, there is a need for decomposing very large data bases into physically or geographically dispersed units and/or integrating existing data bases held in physically isolated nodes into a single, coherent data base that will be available to each of the distributed nodes. In this paper, the design issues and solutions for resource management of data on a DDB are studied. The different aspects of resource management are categorized in the next section. These management issues are part of the issues related to the operational control of a DDB and are con-