An iterative data reengineering approach where the legacy data are frozen for read-only access until the data transformation process to the target database is complete. This approach assumes that the legacy data are the most important part of the reengineering process and focuses on the legacy data structure, rather than its values, during its migration.
Published in Chapter:
Data Reengineering of Legacy Systems
Richard C. Millham (Catholic University of Ghana, Ghana)
Copyright: © 2009
|Pages: 8
DOI: 10.4018/978-1-60566-242-8.ch005
Abstract
Legacy systems, from a data-centric view, could be defined as old, business-critical, and standalone systems that have been built around legacy databases, such as IMS or CODASYL, or legacy database management systems, such as ISAM (Brodie & Stonebraker, 1995). Because of the huge scope of legacy systems in the business world (it is estimated that there are 100 billion lines of COBOL code alone for legacy business systems; Bianchi, 2000), data reengineering, along with its related step of program reengineering, of legacy systems and their data constitute a significant part of the software reengineering market. Data reengineering of legacy systems focuses on two parts. The first step involves recognizing the data structures and semantics followed by the second step where the data are converted to the new or converted system. Usually, the second step involves substantial changes not only to the data structures but to the data values of the legacy data themselves (Aebi & Largo, 1994).