Parallel database systems are complex entities. When teaching about these systems as part of a course in a limited time, one has difficulty providing useful practical experience that gives a deep insight into system behavior and operation. This paper describes a tool for performance prediction that has been developed to aid the visualization of parallel database systems and that is currently being used to support teaching. The tool enables students to experiment with different hardware and software configurations and to view the effects of changes on the performance of the system. The tool provides insight into how data can be placed among the nodes of a parallel machine according to predefined strategies, as well as manually, and provides feedback on the effect of these on throughput and response time. This tool is able to provide a good appreciation of the concepts in a relatively short period of time.