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"Legacy" database migration to a relational DB at the Belgian Ministry of Finance
Guido Tieleman, project leader "ICPC" at the Ministry of Finance declares: "I have got the opportunity to achieve a close follow up of all migration phases and I confirm that the application functionality remained unchanged despite the DBMS change. I am convinced that REVER technology open new flexible evolution perspective for our " integrated tax processing" project.
Confronted to its IT systems diversity, the Belgian Ministry of Finance (SPF Finances) choose in 2005 a new IT strategy. The objective was allowing any application to access any database, independently from the technological platform they are running on. In other words, the new SPF strategy is requiring that any database is accessible (with an access right) by any program running on any hardware.
Looking at the technological aspects, this strategy is making use of an architecture allowing legacy databases to be restructured in DB2 and installed on Sun - Solaris servers. These databases servers are of course accessible from all application servers on which the legacy programs are still running and this, through a high speed bus.
The mission of REVER was to transform and migrate an IDS2 - Bull - GCOS8 database to a DB2 database running under Solaris. The application programs, written in COBOL, will continue to run under their initial BULL GCOS8 system.
So, the job of REVER was to move a database to another technological platform with a change of DBMS requiring specific tools and methods.
The database to be migrated (called ICPC, taxes recovery, perception and accounting system) is a strategic application at the Ministry of Finance. As a consequence, the REVER approach has been to secure each step of the project in order to avoid any risk
In order to meet these requirements, the solution proposed by REVER was articulated in two main phases :
- A first one, called «replication», had the objective to obtain, on the Solaris database server, a DB2 relational database being an up-to-date "copy" of the IDS2 one;
- A second one, called «using the DB2 base», had the objective to adapt the application programs so that they use exclusively the DB2 base, the IDS2 base being deleted.
This approach, approved by the Ministry of Finance, was providing the following benefits :
- It was meeting the security requirements of the migration process. The first phase had indeed a minimal impact on existing applications programs and IDS2 databases which were still running in parallel with DB2;
- It was possible to validate that the DB2 target database was correctly running before final programs transformation;
- It was providing a DB2 database, "rapidly" ready for new developments.
The main results provided by the REVER approach were :
- A real native DB2 target base , optimised and ready for new developments;
- A fully controlled and secured migration process thanks to:
- technical risks identification when related to data, structure, and programs;
- data validation before migration;
- data migration according to a logical approach in order to guarantee their coherence;
- minimisation of the program source code modifications;
- validation of each process step before going to production;
- maximal process automation allowing to shorten significantly the delivery time;
- no freezing of the developments;
- The DB Main repository allowing:
- to obtain a detailed documentation of the application;
- to easily manage the application evolutions after migration.
This project was achieved in collaboration with the Bull Group.