Day-to-day business involves not only regular development and maintenance work, but constant adaptation of the applications to the system environment as well. With the ADS generator system, the Datenzentrale Baden-Württemberg has time and again managed to carry out these migrations silently, cheaply, and quickly.
The Datenzentrale Baden-Württemberg, founded on September 1st 1971, supplies in cooperation with the municipal and local data computing centers 1,111 communities and most of the 35 counties of Baden-Württemberg with application software for registration management, taxes, building authorities, social affairs, human resource management and accountancy; for the motor vehicle registration, management information systems etc. The most current projects are special offers for e-government and e-authorities services.
Thus, the Datenzentrale Baden-Württemberg is the market leader in providing municipal branches software in Baden-Württemberg. However, numerous contented users more and more avowed the advantage of sophisticated software. The number of customers from other federal states increases consistently. Many communities of the federal state of Sachsen are supplied with this software as well.
Of its 140 members of staff, 80 are engaged in the field of software development and maintenance. They use an IBM system under VM/CMS for MVS/CICS and DB2. Changes have to be made in response to new technical and statutory requirements. In addition, new techniques have to be implemented in the applications, and the applications have to be incorporated into new the environments.
At the end of the seventies, a decision was made to convert the batch process as far as possible to dialog. The OSSY dialog system of Heyde & Partner in Bad Nauheim was chosen for this. With OSSY, Delta/ADS came to the data centre. The advantages of Delta/ADS were soon recognized, and were fully exploited. Standardization of the interfaces and the program frameworks in macros made development very flexible and independent of the physical environment. Thus, for example, there was no need for developers to undergo CICS training. And one great advantage in the maintenance of applications resulted from the introduction of structured programming, supported by Delta/SPP, long before COBOL 85 and VS COBOL 2 from IBM.
This conversion, which took less than three years, laid the basis for future silent migrations - silent in that the application programmers were not involved in them. As a rule, a two-man team prepared these conversions in a short time by adapting and testing the macros for interfaces and program frameworks. There was no need for the programmers to be trained. And development of the application did not have to be disturbed or interrupted by a large-scale migration project.
There were three reasons for converting the existing applications to VS COBOL 2: the programs would be re-entrant-capable under CICS; the address space would be expanded under MVS/XA to 16 MB; and this would lead to improved performance.
New addressing techniques with base locators had been introduced, together with new CICS commands. Because of the relocation and standardization of the I/O interfaces in macros and program frameworks, the time spent on changing and testing about twenty macros was reduced to four man-weeks. Following this, about 30,000 programs were regenerated in six months. The results of the generations carried out overnight were checked the next day without the need to interfere with the day's business. Without Delta, the data centre would have had to set aside several years for this conversion alone.
With ADS, about 30,000 programs were migrated, and performance was improved, in only six months. The programs are now running three times faster than they were before.
With this conversion, as in the case of the COBOL migration, the macros were changed in one day, and were thereafter tested in no more than four. The required changes never came to the surfaces. And the migration went by almost unnoticed. Neither a project nor a budget was needed for the migration of about 30,000 programs.
Initially, the OSSY dialog control ran for the MVS/CICS environment. Later, the AS/400, VAX, and Windows platforms were added. In some cases, these platforms require drastic changes to the control logic. As the interface between the application modules and OSSY has also been implemented in the form of Delta macros, it is sufficient here as well merely to adapt and test these macros, and to regenerate the applications.
The file interface to VSAM has been implemented with Delta/FILE. This has also meant a reduction in the amount of training needed for programmers in the use of the GET and PUT logical I/O commands. In addition, the introduction of IMS/DB and the use of IMS/DB macros from Delta/ADS also meant that the interface to the application programming remained unchanged. In one year, about six hundred programs have been converted to IMS/DB and rewritten. As IMS/DB has proved to be too expensive and its administration to involve too much time and effort as far as the data centre is concerned, its introduction has been stopped.
Thanks to ADS, however, this experiment with IMS/DB was easy to cancel, and it was possible to continue to use the six hundred programs involved. Almost overnight, they were changed back to VSAM by means of regeneration.
Two years ago, it was decided to develop the application for population matters with DB2. Once again, the question was whether to page out the SQL commands to macros, or to implement them in the programs. The Datenzentrale Baden-Württemberg opted for the Delta/FILE interface for DB2, because this solution did not require the developers to undergo extra training. In doing so, it accepted the need to generate separate macros for updates. Specifying the minimum number of places to be changed in the Delta standard macros and documenting the changes in the macros concerned are part of standard program development work. By the end of 1998, about 1,000 dialog programs will have been developed, using eight developers and two macro programmers.
It was established with the inventory and a first roughly estimated analysis, that some data portfolio can remain with a 2-digit date at first others however must be expanded. Simultaneously, the temporal decoupling of the changeover of the data stock and programs as well as a minimal blocking time of the programs to be changed was a matter of top priority for the data centre.
10,000 modules are approximately concerned. Also here, the usage of Delta products proved to be a significant advantage with the standardization of interfaces: the file macros were extended according to the time-window technology. Hence, the input of the date was extended to four digits, while the output of the date was minimized to two digits. A runtime key was in charge of managing of whether a particular files was to be altered or not.