Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide

Compiling your DLL source

You can compile your source files to create a DLL in the same way that you would compile any other file (using the PLI command) with one exception--you must compile at least one file with the DLLINIT option. You can compile every routine in a DLL with the DLLINIT option; however, no routine compiled with DLLINIT can be linked into an EXE.

You might also want to compile your programs with the option XINFO(DEF). This option creates a .DEF file for each program. These .DEF files are essential to preparing to link your DLL.

Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide