Jobstream simulation using a channel multiprogramming feature

摘要

A rotational position-sensing feature designed for direct-access devices reduces the time a hardware channel is busy searching for disk records. This is accomplished by electronically dividing the track of a disk into equally spaced timing sectors, using new hardware commands to access desired sectors. When an I/O record located some distance away in rotation is requested, the channel disconnects to allow concurrent servicing of requests from other devices. Through a combination of hardware and software, multiprogramming at a channel/disk level is achieved, thus improving channel performance.

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In this study, overall effectiveness of the feature was evaluated in a multiprogramming environment. Simulation at high and low levels simultaneously required a unique approach in the models. Hardware models were based on close tolerances and exacting operations, while software jobstream models were more generalized. The objective was to simulate a typical jobstream in a typical multiprogramming environment on specific hardware.