Trace-driven study of CMS file references

Abstract

This paper presents a detailed study of file reference patterns by users of a VM/CMS interactive system. The data were collected from two different IBM locations via CMON, a CMS monitoring facility. We present background information about the CMS file system, the CMON program, and our data-reduction programs, as well as a discussion of the results. Some earlier studies of this type have been restricted to a static analysis of the existing files. However, as is shown in this paper, a static analysis does not reliably reflect dynamic file reference behavior. By using both static statistics and dynamic statistics, it is possible to better understand how file systems are used, to evaluate possible changes, and to provide distribution parameters for modeling. More recent studies of other interactive systems have measured dynamic activity patterns. We compare our results with these when appropriate.