You are basically correct. The DDS doesn’t have arrays so you might format sales as
A Sales01 9S 2
A Sales02 9S 2
A Sales12 9S 2
In RPG IV you can overlay the data with an array for the program
These you can put into a copy book and copy into every program
D MySalesds E DS EXTNAME(mySales)
D SalesAR like(Sales01) Dim(12)
D overlay(MySalesds : 54)
where 54 is the first byte the data in the physical
Since SalesAR overlays the 12 sales fields in the file
The field values always equals the array values ..
Sales01 will always be equal to SalesAR(1) etc.
I’m not sure if all of this will work in V4R4.