A simulation model representing the OS/VS2 Release 2 Control Program

Abstract

Traditionally, successful simulation modeling as a design evaluation tool and a performance evaluation vehicle has been confined to small subsystems of an operating system. The effort involved in modeling a total operating system usually has been prohibitive. Those models that were created tended to be too complex to use, and their architectures reflected existing systems rather than future systems.

This paper describes techniques used for CSS modeling of the OS/VS2 Release 2 Control Program prior to the existence of the full systems. The model was conceived to operate at the system level, representing a functional rather than an imitative approach to simulation. It gives a general overview of the modelling techniques used and then discusses a salient feature of the model, representation of the relocate environment (paging). A section is devoted to discussion of the novel tracing methodology used with the model. The validation approach used for the model is described, the basis for which is a comparison of comparable real system runs and trace driven model runs.