Supporting large scale applications on networks of workstations

The extension of the ISIS distributed programming system to support large-scale distributed applications by providing hierarchical process groups is discussed. The present version of ISIS is limited to relatively small-scale applications, containing fewer than 50 workstations. The principal idea is to incorporate hierarchy in the program structure and exploit this to limit the communication and storage required in any one component of the distributed program. This approach seeks to maintain the advantages of virtual synchrony, while controlling those costs that grow as the size of a distributed application increases