You can directly debug Link Library projects that produce a single .dll file, and indirectly debug Link Library projects that produce multiple .dll files.
To directly debug Link Library projects that produce a single .dll file, you need to identify the entry point for this type of project, which is either the first COBOL program passed to the linker when the .dll is created, or the program specified in your .def file, if present. If you do not use a .def file, the programs are linked in the order in which they appear in the project file, which is alphabetical order by default.
To debug Link Library projects that produce multiple .dll files, that is, each COBOL program in the project compiles to a separate .dll file, you must specify one of the output .dll files (or an executable that loads it) on the Debug tab in your project properties. To do this, set Launch to Executable and then specify the path to the file in the Executable field. See Debug Properties for details.