Skip to content

Rules of Thumb are easily learned procedures for estimation based on experience or common knowledge. This presentation will examine several ROTs related to the performance of applications and systems. The ROTs will range from those that have and have not stood the test of time.


Since the early days of the mainframe, performance analysts have been developing and using Rules of Thumb to aid in their quest to explain current system behavior and plan for the future. In the late 1980s, a number of CMG papers described ROTs that were focused on mainframe usage, applications and performance. Since then, with the rise of client/server, distributed systems and the Web, the breadth of ROTs has expanded.


Most ROTs were developed from observations or (queuing) theory. What makes this an interesting topic is to understand the reasoning behind individual ROTs; i.e., what was the train of thought that led to the development of a ROT.

However, as with most things related to technology – the world changes. Some of yesterday’s ROTs are no longer applicable. There are other ROTs that have been revised over the years to account for technology changes. And then there is a set of ROTs that work today just as well as they worked years ago.


This presentation will examine a number of ROTs that fall into three categories: relics of the past, updated and revised to address today’s technology, and those that have successfully stood the test of time.

Presented by