An Introduction to Variable Field Lengths in RPG

RPG experts Jon Paris and Susan Gantner explain new capabilities available with the Fall 2019 IBM i TR

We first wrote about variable length fields back in 2002. We decided this is a good time to revisit this topic for a number of reasons:

1. As more and more people make use of SQL to define their tables, we see a corresponding increase in the usage of variable length fields. If those tables are to be used with native I/O operations, RPGers need to understand how to deal with them.
2. We’ve recently seen a number of programmers moving to IBM i from other platforms, and for them, variable length fields tend to be the norm and so naturally, they use them on IBM i as well.
3. Variable length fields offer many benefits to the RPG programmer as they can simplify and clarify logic, improve efficiency and just make things “better” all around.
4. Last, but by no means least, when we reviewed our original article we found that it was all fixed-format RPG—including the calculations! *Shudder!*

Defining Variable Length Fields in RPG

Let’s begin at the beginning. Variable-length fields can be defined either internally within your RPG program, or on the database. We’ll get to the database aspects later; for now we’ll just look at defining and using variable length fields within RPG. 
Definition within a program is a simple matter. The first example shows the old D-spec style definition where the keyword VARYING is used. In the new free-format (and all of our subsequent examples will use that format) you simply specify Varchar as the data type. These two field definitions accomplish basically the same thing:
 

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