Various transaction types are first assigned to host systems to balance CPU utilizations. We then distribute the shared files among host systems to minimize total remote file accesses. Queueing network models for our distributed systems are constructed from a set of submodels of the host systems, of the local area network, and of the file servers if any. Model parameters are derived from our workload data, measured in an interactive transaction-oriented business system. Two examples are provided to show how the configuration of a local area network-based distributed system can be designed by using our workload data.
Attempts are next made to capture in our queuing network models the difference in resource demands during the preparation phase and the execution phase of a typical transaction. As a result, we introduce the special class of phase-free queueing network. It is shown that a general product-form queueing network can be reduced to an equivalent phase-free product-form queueing network. It is also shown that the per-class throughputs, mean queueing time, and mean queue length in the original network can be calculated from the values of the aggregate indices of the phase-free network.
Lastly, a special class of local area network-based distributed systems, that of the workstation-based systems, is examined in some detail. Workload clustering is proposed as a method for reducing the number of chains in the model to make it more tractable mathematically. File server design issues are investigated, and design guidelines are recommended based on workload data and performance goals.