AS400
to Open, Industry Standard Systems
Design
|
COBOL | DDS
| Transaction
Files | DMS Files
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Started questionnaire
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
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