Importance

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Abstract

A method and apparatus that permits creation, reading and modification of 3GL application programs by SQL requests. A catalog is created by selecting source programs from 3GL application data for which file definitions are to be extracted, identifying specific files within the selected source programs to be processed, extracting appropriate schema from the selected files, and recording the appropriate schema in a catalog. Once the 3GL-specific data schema contained in the application source has been extracted and stored in the catalog, the relational database which is to be based upon the data represented by the 3GL schema is defined and stored in the system catalog so that tables in the relational database may be accessed by a runtime SQL database engine. Further, both 3GL data and relational database data may be modified and maintained with a single tool set. After the catalog is created, the invention uses the catalog to process SQL requests in order to access the relational database representation of the 3GL data by parsing the SQL query request, generating a set of possible execution plans for manipulating the relational form of the data, selecting an optimal plan based upon information provided from the system catalog, and executing the plan by servicing the SQL request for relational data from the underlying 3GL data files described in the system catalog.

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First Claim