Modeling of the interactive usage of VAX/VMS

Abstract

Queueing networks are used widely to analyze the performance of multiprogrammed computer systems. A major application of a queueing model is to estimate performance quantities in a future time period for which no directly measured data are available. In this paper a closed queueing model for the interactive usage of VAX/VMS which uses swapping and demand-like paging as a memory strategy is proposed. In this model, swapping activities are represented by state dependent routing probabilities proposed by Chen and paging activities represented by I/O operations such as read I/O``s. To obtain an approximate solution of the model, Chen``s algorithm modified by adding some steps which estimate swapping activities is used. And then the thesis shows a validation of the proposed model. Using the validated model, performance quantities for a changed workload or a reconfigured VAX-11 system are predicted, which are used for capacity planning to meet anticipated increases in an installation``s workload.