MARKOVIAN AVAILABILITY MEASUREMENT WITH TWO TYPES OF SOFTWARE FAILURES DURING THE OPERATION PHASE
Koichi Tokuno, Shigeru Yamada · International Journal of Reliability Quality and Safety Engineering · 1999
This paper develops a plausible software availability model considering two types of failures during the operation phase. The first type is caused by the faults that could not be detected/corrected during the testing phase and the second type caused by those introduced by deviating from the specification during the operation phase. The former and the latter types of software failure-occurrence phenomena are described by a geometrically decreasing and a constant hazard rate, respectively. This model also describes the imperfect debugging environment in which a debugging activity does not always remove a fault perfectly. Taking notice of the cumulative number of faults corrected during the operation phase, we use a Markov process to describe the time-dependent behavior of the software system. Several quantitative measures of software system performance are derived from this model. Finally, numerical examples are presented for illustration of software availability measurement.