File Design Fallacies

The CAM project at LSE is investigating a computer-assisted methodology of developing data processing systems; the project is currently financed by the Science Research Council. The present area of research is the development of prototype software to assist the systems designer in structuring programs and files to satisfy denned data processing requirements on a given computer configuration. While investigating the methodology of systems design, it became clear that various false rules of thumb are widely used in practice; this paper attempts to disprove these rules. Martin (1967), Losty (1969), Daniels and Yeates (1969) are among the more well-thumbed authors to publish rules based on the hit ratio (or activity ratio) of a file; this parameter measures file activity for a batch-processing run as