When you add an existing AcuBench program to a new project, or copy a program from one project to another, it is a good idea to verify that any DLT files referenced by the program exist within the project before you attempt to generate the program. Any time a program contains data set definitions, you will need the data layout file and its associated FD and SL COPY files to successfully generate and compile that program.
If you generate a program before all of the DLT files that it needs have been added to the project, AcuBench identifies missing, required data fields and adds them to Working-Storage. Later, when you add the missing DLT to the project, you will receive errors caused by the duplicate field names. This can be solved by deleting the duplicate names from Working-Storage, but it's preferable to avoid the problem altogether.