Effectiveness of maintenance

This paper pays particular attention to three major areas: inspection effectiveness, repair effectiveness and maintenance induced failures. These three areas are frequently ignored not only in the design of the system but later during the operation of that system. It is often assumed that inspectors are infallible - they will always see a crack if one is present and would never reject a component unless it was in an unsatisfactory condition. However, instinctively, although not necessarily with any mathematical rigour, the most likely time for a computer program/system to fail is shortly after it has been "enhanced". Although it may be difficult and, in some cases, even impossible, to quantify these effects precisely, it is nonetheless important to be aware that they exist, to understand how they may affect the overall operational effectiveness of a system, and what steps can be taken to avoid them.