Throughout the life cycle of a real-time, distributed computer system, numerous situations arise which require access to detailed system performance information. One important type of performance information is known as data coverage. Data coverage is the process whereby all ranges of values for a particular variable in a piece of software have been exercised. Data regarding variable values can be very useful in determining the correctness of program execution. This project investigated the design, cost and usefulness of adding a data coverage performance evaluation capability within an existing Navy weapon system. The target system used is a real-time, loosely coupled distributed computer system. Experiments were created by writing programs in a high level language and executing the programs on the target system. Several of the programs contained "seeded" errors. Experiments were monitored and data was collected by an existing performance evaluation system. The data was collected in a real-time, non-interfering manner and evaluated off-line. The off-line evaluation was accomplished by modifying an existing software package. The package did not include any capabilities for producing a data coverage report. Therefore, it was necessary to enhance the software package such that a data coverage report was created. A description of the investigation and the various factors used for the evaluation of a data coverage capability, the design proposal, and the cost analysis are included in this report. / Master of Science