Why Do Computers Stop and What Can Be Done About It?

An analysis of the failure statistics of a commercially available fault-tolerant system shows that administration and software are the major contributors to failure. Various approaches to software fault-tolerance are then discussed -notably process-pairs, transactions and reliable storage. It is pointed out that faults in production software are often soft (transient) and that a transaction mechanism combined with persistent processpairs provides fault-tolerant execution -the key to software fault-tolerance. DISCLAIMER This paper is not an “official” Tandem statement on fault-tolerance. Rather, it expresses the author’s research on the topic. ______________________ An early version of this paper appeared in the proceedings of the German Association for Computing Machinery Conference on Office Automation, Erlangen, Oct. 2-4, 1985.