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Universal Operational Analysis library for performance engineering.

PETER J. DENNINGComputer Sciences Department, Purdue Unwers~ty, West Lafayette, Indiana 47907JEFFREY P. BUZENBGS Systems, Inc., Box 128, Lincoln, Massachusetts 01773

Queueing network models have proved to be cost effectwe tools for analyzing moderncomputer systems. This tutorial paper presents the basic results using the operationalapproach, a framework which allows the analyst to test whether each assumption is metin a given system. The early sections describe the nature of queueing network models andtheir apphcations for calculating and predicting performance quantitms The basicperformance quantities--such as utilizations, mean queue lengths, and mean responsetunes--are defined, and operatmnal relationships among them are derwed Following this,the concept of job flow balance is introduced and used to study asymptotic throughputsand response tunes. The concepts of state transition balance, one-step behavior, andhomogeneity are then used to relate the proportions of time that each system state isoccupied to the parameters of job demand and to dewce charactenstms Efficmnt methodsfor computing basic performance quantities are also described. Finally the concept ofdecomposition is used to stmphfy analyses by replacing subsystems with equivalentdevices. All concepts are illustrated liberally with examplesKeywords and Phrases" balanced system, bottlenecks, decomposability, operationalanalysis, performance evaluation, performance modeling, queuelng models, queuelngnetworks, response tunes, saturation.