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Program Conversion - Mainframes - Schema - Relational Database


In the event that the mainframe application is already using a relational database (DB/2 or Oracle), the migration path changes considerably.  While a schema is defined for the present system, it may contain remnants of earlier file or table structures, and the migration may be a good excuse to clear these out.  State-of-the-art relational databases provide replication, which means that a Windows server based ASP.NET application can effectively update the mainframe tables.  In such circumstances the conversion is not an 'all-or-nothing' proposition: new code on the Windows server simply shares data with the existing mainframe apps.

If the intent is to eventually shut down the mainframe, the schema-first path is still the best to take.  One good approach is to duplicate the existing schema in SQL Server 'as-is', which will identify one-to-one issues.  Many of these would be related to mainframe storage in EBCDIC format, if the data is still being represented that way.  For systems that are usually accessed through web applications, the mainframe data is probably already being stored in ASCII.

The next step is to create a 'native' database that represents the 'new' schema.  This is the record organization that is the 'best fit' for an ASP.NET-based system.  As described elsewhere, this should be used immediately for ad-hoc reporting, so that users are already becoming familar with the new record structures and data contents.

The only remaining issues at that point are whether to synchronize the mainframe database and the SQL Server instance through replication, triggers, and stored procedures.  Doing so allows development to occur at a more measured pace, however it also forces a slower migration since all the business rules and constraints have to be enforced in two disparate databases.  This is likely to be easy with simple master table maintenance, and get progressively more complicated as the programs drill into more detail and operate within more constraints.

For those that feel like their system is way overdue for an upgrade, please call 210-734-5575 for free initial consultation.

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