IBM AS400 to Open Systems

Unicon's IBM/AS400 to Open Systems migration solution is designed to allow AS400 COBOL users to migrate their AS400 COBOL source code and Data Display Specifications (DDS) to Open Systems COBOL. The conversion product, named UNI/400,   is used to generate Open Systems COBOL programs. 

DESIGN : UNI/400 consists of two utilities - CBL/400 and DDS/400. These two utilities address the major source code issues for people needing to migrate AS400 COBOL applications to Open Systems COBOL. These major issues are the AS400 COBOL programs and the Data Display Specification (DDS) or screen specs.

COBOL : The CBL/400 utility converts AS400 COBOL source code to Open Systems COBOL source code running under UNIX and resolves the major differences between AS/400 COBOL and Open Systems COBOL, namely the transaction files and the DMS files.

DDS : The AS400 DDS specs are converted to Open Systems COBOL programs utilizing the Open Systems COBOL screen section to display information on the workstation. DDS/400 generates the Open Systems COBOL code from templates that can be used to implement custom standards for the converted programs, thereby allowing the user maximum flexibility and control in the design of the output.

TRANSACTION FILES : AS400 transaction files are used to communicate with workstation devices and are accessed in concert with AS400 DDS modules. As transaction file definition and transaction file statements describe workstation operation on the AS400, so does the transaction file record definition and calls to the DDS manager under Unicon's UNIX Open Systems COBOL runtime. Essentially the AS400 COBOL program will populate the transaction file record with data and WRITE information to the workstation via a DDS module or extract information from the workstation after a COBOL transaction file READ statement has received information from the DDS module. CBL/400 converts all TRANSACTION file READ, WRITE and REWRITE statements to CALL statements, OPEN and CLOSE statements are deleted. These call statements transfer control to the DDS manager, passing transaction file parameters. The DDS manager then hands the parameters on to the appropriate (DDS/400 converted) DDS module.

DMS FILES : AS400 DMS files are described, primarily, outside of the COBOL programs. An AS400 COBOL file definition does not describe a file as understood by most COBOL dialects, instead it describes the access path into the database that this particular program requires. This presents a problem for COBOL because COBOL requires that the program file definition match the external file definition exactly. UNI/400 solves this problem by adjusting the Open Systems COBOL runtime system by adding "I-O vectors" so the COBOL file definition does not need to match the physical file definition. In addition UNI/400 contains an "OPEN" subroutine that will provide AS400 style verification between the physical file definition and the COBOL program file definition. This subroutine will also resolve the external file name for the file.

We trust the above provides some insight into our AS400 COBOL to Open System conversion services. For a more in-depth look into this conversion, please contact us in order that we may run through the process with you and ascertain your needs and targets. We will be pleased to work to provide you with the best possible migration path to installing open systems architecture technology