Achieving correct changes is the dominant activity in the application software industry. Modification of database schemata is one kind of change which may have severe consequences for database applications. The paper presents a method for measuring modifications to database schemata and their consequences, by using a thesaurus tool. Measurements of the evolution of a large-scale database application currently running in several hospitals in the UK are presented and interpreted. The kind of measurements provided by this in-depth study is useful input to the design of change management tools.