File access characterization of VAX/VMS environments

A comprehensive analysis of file access behavior of several commercial production VAX/VMS environments, based on detailed I/O traces, is presented. The characterization focuses on file control operations (such as opens and closes) which are often expensive in both processing and I/O requirements. The motivation for this analysis is the need to design good data management algorithms for distributed file systems. These algorithms are particularly important for managing client caches. Most of the operations for managing client caches are performed on file opens and closes. The authors present quantitative data on the number of file opens and closes, their timing characteristics, and their declared intent to allow sharing or have exclusive access. The precise dynamic sharing of files is examined.<>