Data independent revisions to data base definitions



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This thesis deals with the question of how to modify a data base definition independent of values which have been entered into the data base. Specifically an attempt was made to derive a scheme which would allow definition modifications of an existing data base to occur with a minimum of reorgization within the data base. The data base management system chosen for examination of definition modifications was the Remote File Management System. Possible modifications to the definition of a data base consist of changes in data descriptions, the addition or deletion of data descriptions, and changes in the order m which data is related to other data in the data base. Each of these definition modifications is examined in depth and a scheme involving minimal reorganization within the data base is thoroughly detailed tor each modification. Each scheme is then compared to the only other known method of handling definition modifications, completely unloading the data and reloading it using the modified definition. In every instance the new schemes for definition modification in the Remote File Management System were found to be superior to the unload-reload method.