Shared library files are linked into system executable files. They are loaded when the system executable is loaded and run. They cannot be executed themselves. They can be shared between processes. If multiple copies of the same shared library are used at the same time, the operating system shares the procedural code and creates separate data areas for each process. This includes sharing any COBOL procedural code linked into the shared library file.
Shared library files have the prefix lib, and the extension .so; for example, libmyprog.so. On HP-UX PA-RISC, the extension is .sl.
Programs are compiled using the cob -Z command; see COBOL System Interface (Cob) and Linking to System Executables for details.