International Business Machines Corporation has a lot of information to index and so it's not surprising that folks get lost trying to get basic documentation. Here's my guide to a starting set of manuals for ILE RPG programming. This page is tailored to IBM i 7.1 (also known as V7R1M0); I will develop pages for other versions of the operating system as time permits.
Note that these links will display or download the manuals in PDF format. (Depending on your browser, you may have to right click and select "Save As..." to save the manual.) I suggest that you do so and use them from your computer hard drive. In some cases, IBM includes the manuals in HTML format and I leave it as an exercise to the reader to find those.
All of these manuals are written in American English. Supposedly, there are versions written in other languages but I couldn't find them quickly. Let me know if this is a problem for you and I will see what I can do.
ILE RPG Reference 7.1 [PDF] This is a reference manual; it describes the language but really doesn't tell you how to use it.
ILE RPG Programmer's Guide 7.1 [PDF] This manual explains how to do things with ILE RPG.
Of course, you will need to work with files. For database files, there are four manuals:
Database SQL Reference 7.1 [PDF]
Database SQL Programming 7.1 [PDF]
Database Programming 7.1 [PDF]
DDS for Physical and Logical Files 6.1 [PDF]
You can use either SQL or DDS to define your files and their characteristics. They are somewhat interchangeable.
For display files, use DDS for Display Files 6.1 [PDF].
For printer files, use DDS for Printer Files 6.1 [PDF].
Next, you're going to need to code Command Language (CL) programs for your ILE RPG programs. The manual for that is CL Overview and Concepts 7.1 [PDF].
Finally, there's the Integrated Language Environment part of ILE RPG. (ILE reminded me of the linkage editors we had in the 1970s so I jokingly refer to it as "Integrated Linkage Editor.") You can write useful programs without knowing a thing about ILE. But, when you're ready, you'll want to look at ILE Concepts 7.1 [PDF].
While researching this blog entry, I did find a master list of version 7.1 manuals. Go to the IBM Infocenter at this link and click on "PDF files and manuals".