DYL-PDS was an add-on option to DYL-280 (now VISION:Eighty).
DYL-PDS, and another option, DYL-TABLE, were bundled into DYL-280 to create DYL-280 II (now VISION:Results).
When bundled, these functions were made internal and given command syntax rather than external CALLs.
Chapter 23 of the r6 Reference Guide documents the PDS function and its syntax.
You can copy the old DYLPDS module or concatenate loadlibs to avoid making changes to the application for the new syntax.
However, DYLPDS as a module is no longer supported and forces use of storage below the 16M line, so it is preferred that the application be modified to use the new syntax.