PETRI-NET MODELING AND RELIABILITY EVALUATION OF DISTRIBUTED-PROCESSING SYSTEMS

A Petri Net model for the evaluation of reliability for the execution of a computer program in a distributed processing system (DPS) is developed. The execution of a program in a DPS may require access to several files residing at different sites and communication paths between several node pairs. The dynamic behaviour of the system under consideration is represented in the form of token movements within the model. Then, by using the reachability, firing, and marking concepts of Petri Nets, an algorithm is developed to study the two important reliability measures, namely, distributed computer program reliability (DCPR) and distributed processing system reliability (DPSR). The proposed algorithm is efficient in the sense that it directly generates all possible sets of path identifiers for the accessibility of a file which resides at more than one place and is required for the execution of a computer program residing at some other place without evaluating minimal S-T-paths for all S-T-connections. The developed algorithm has been implemented on a minicomputer.