THE PROPAGATION OF UPDATES TO RELATIONAL TABLES IN A DISTRIBUTED DATABASE SYSTEM

The problem of applying update operations to relational tables under t he supervision of a distributed database management system is consider ed. A model describing the minimal cost propagation strategy of an upd ate request to all copies of the relevant relation is offered, and tak es the form of an integer linear program. A user request is issued at a given site in the network, specifying an amendment to the informatio n comprising some particular logical data set, or relation. Replicatio n of data admits the possibility of relations being duplicated, with s everal distinct copies disseminated amongst various processor sites; s ynchronization of replicated information to preserve its consistency c ommands that the alteration be applied uniformly to all. The update re quest must therefore be communicated to each site possessing a copy of the relation to which it refers. This task demands the utilization of limited system resources; data transmission channels convey the updat e signal between sites, and processors apply the operation to stored c opies of the particular relation to be changed. The ultimate goal is t herefore to choose from all possible update propagation strategies one that achieves the smallest total cost. The formulation initially atta ined by considering the role of an isolated processor in a valid strat egy contains some constraints that are nonlinear. However, by introduc ing new decision variables and reconsidering the offending inequalitie s, the model can be transformed to realize an optimization program ent irely linear in structure.