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Abstract

A practical mathematical algorithm is used to solve the so-called 'File Assignment Problem' (FAP). The FAP is partitioned into two sequential optimization problems, called the macro model and the micro model. The macro model is solved by a Non-Linear Programming Model (NLPM) and a Queuing Network Model (QNM). The NLPM takes as input detailed information on the computer system configuration and performance characteristics down through the DASD level, and, using the QNM as its objective function evaluator, determines the 'optimal' DASD relative access rates as output. The micro model is solved by a Binary Linear Programming Model (BLPM), although the QNM is also involved to help determine the BLPM stopping criteria. The input to the micro model consists basically of the output from the macro model, together with statistics on the access rates of the various files in the computer system. The output from the optimization is an 'optimal' assignment of files to DASDs. The micro model algorithm can be utilized in either an unlimited file movement mode or a limited file movement mode, the former being used when the computer system undergoes a major reconfiguration while the latter is used on a once per week basis. The BLPM is solved by a 'neighborhood escape' type heuristic. The procedure provides a real-world, practical solution to the FAP resulting in significant increases in performance.

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