This paper describes a simple yet effective distributed database model that simulates database utilization in the distributed data processing environment. The model is table driven such that database access requirements, file location, and other information necessary for defining the database environment are set up internally in several tables. Each database transaction is defined and represented by a transaction flow diagram (TFD) and a sequence of TFDs representing a operational scenario is input to the model. The model "executes" input TFDs by looking up tables that specify their data file access requirements. While executing TFDs, the history of database usage is logged and various statistics are gathered. The performance data are used to measure database access overhead, characterize database workload, and fine-tune performance by reallocating files. The model has been implemented in Fortran on the VAX 11/780 and has been used for both measuring the given database performance and analyzing sensitivity to design changes. It has proven to be an effective tool for analyzing design effectiveness of distributed databases.
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