This abstract presents an approach, supported by an industrial case study, to data reengineer a sequential file system to a relational database with multiple, linked, normalized tables with properly delimited fields of the correct data type. In addition, the data access logic of the underlying COBOL program is modified to access the newly reengineered relational database rather than the sequential files. Our approach assumes the presence of a master-file update function within the COBOL program; multiple file records with several fields of alphanumeric type; and corresponding temporary records with matching but incongruent fields of different data types.