Release 10.1A: OpenEdge Application Server:
Developing AppServer Applications

Minimizing the effects of schema changes

In the traditional client/server model where all Progress 4GL clients are connected to a database, database schema changes can invalidate r-code run by the client. In contrast, by designing your Progress 4GL client application to be independent of database schema, you can use the AppServer to minimize the effects of schema changes by masking the changes from the client application.

The following list identifies specific techniques you should use to shield these schema changes from affecting client applications:

Set up database access so that it is accomplished entirely through AppServer agents (the client is not connected to the database and all records are transferred from the AppServer agent through temp-table parameters).
Avoid using LIKE syntax for temp-tables and variables in client application code and in procedure parameters for remote procedures.
AppServer agent code must map data based on the new schema to the existing procedure parameters for the remote procedure.