Loading a Dynamic Link Library Built as Native COBOL Code

.dll files (which are built as native COBOL code) must be loaded into memory before they can be used. If you statically link a .dll file it is loaded automatically before your application is run. If you use dynamic linking, your program should load each .dll file as necessary before attempting to call entry points in it:

• If the .dll file contains a single public entry point and you use the name of the .dll file in the CALL statement, the file is loaded automatically when called.

  For example, if a file mydll.dll contains a single public entry point, the file is loaded and the call executed by a CALL "mydll" statement.

• If the .dll file contains several public entry points, use the SET procedure-pointer-name TO ENTRY program-name statement before you call the entry point. For example:

  set mypointer to entry "mybigdll"
  call "My-third-entry-point"

You need to load a dynamic link library the first time you use it only, unless the .dll file is no longer in memory.

A .dll file is automatically removed from memory when a COBOL program within it is canceled and this results in all COBOL programs in the .dll file being either in an uncalled or a canceled state.

For example, consider a .dll file called sub.dll which contains three COBOL programs: sub.cbl, sub1.cbl and sub2.cbl.

1. Program sub.cbl is called from the main program.
2. Program sub2.cbl is called.
3. Program sub.cbl is then canceled.

   The .dll file is not removed from memory because sub2.cbl has not yet been canceled.

4. Program sub2.cbl is canceled.

   The .dll file is removed, because all programs within it are now either canceled (sub.cbl and sub2.cbl) or not called (sub1.cbl).

The way you load OO .dll files depends on whether they contain a single class or several classes.