Strategies for Creating Service Programs - IBM - RPG

When creating a service program, you should keep in mind:

1. Whether you intend to update the program at a later date
2. Whether any updates will involve changes to the interface (namely, the imports and exports used).

If the interface to a service program changes, then you may have to re-bind any programs bound to the original service program. However, if the changes required are upward- compatible, you may be able to reduce the amount of re-binding if you created the service program using binder language. In this case, after updating the binder language source to identify the new exports you need to re-bind only those programs that use them.

TIP If you are planning a module with only subprocedures (that is, with a module with keyword NOMAIN specified on the control specification) you may want to create it as a service program. Only one copy of a service program is needed on a system, and so you will need less storage for the module. Also, you can copyright your service programs using the COPYRIGHT keyword on the control specification.

Binder language gives you control over the exports of a service program. This control can be very useful if you want to:

• Mask certain service program procedures from service-program users
• Fix problems
• Enhance function
• Reduce the impact of changes to the users of an application.

See “Sample Service Program” for an example of using binder language to create a service program.