Reengineering VSAM, IMS, and DL/1 Applications into Relational Database
Most reengineering requires either a rebuild of the application to use relational database or two parallel database systems: the legacy database and a relational copy. A more pragmatic and effective approach is one database that provides both relational and navigational access methods. The legacy database DML is supported by a “transparency”: software to map the legacy DML to the new relational database’s navigational DML. Existing applications continue to run untouched while new relational tools and technologies are used against the same data. End-users and programmers get immediate client/server SQL access. Programs can be modified or replaced to take advantage of relational technology at leisure in an incremental manner. A methodology is described here for an incremental approach to do this using the transparency technology. The appendix provides technical detail to demonstrate how one example of a transparency is implemented.
KeywordsRelational Database Integrity Constraint Business Rule Legacy Application Legacy Data
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