SNAP/SHOT (System Network Analysis Program-Simulated Host Overview Technique) is a discrete simulation of a network and/or host model available through IBM at the Raleigh System Center. The simulator provides an analysis of a total IBM Communications System. Input data must be obtained from RMF, SMF, and the CICS Analyzer to determine the existing environment and from analysis and users on anticipated applications and their volumes. The simulator permits the introduction of numerous variables in order to evaluate the impact of altering resources such as memory, software, paging devices, CPU's, lines and terminals, and altering volumes of transactions, message mixes, and size of transactions. Indiana University has used SNAP/SHOT twice to identify the volume of transactions that was supportable on existing equipment and the changes that would improve performance. After the first run, a group was assigned to optimize some transactions and additional memory was added to reduce the paging rate. The second run was made to see what had been accomplished and to simulate simultaneous student registration at the six small campuses, and then at the large campuses. Graphs and charts identify the many variables utilized in the processing of Indiana University data and show the results obtained. (Author/JEG)