Libraries

Your product can use various type of libraries:

z/OS® Language Environment® libraries
Because z/OS Language Environment is upward-compatible, a program that runs on a lower level of z/OS Language Environment can also run on higher levels without being relinked or recompiled. You can optionally recompile your programs, if you want to take advantage of new features that are introduced to z/OS Language Environment.
Your own libraries
If your program uses your own libraries, you can statically bind the libraries with the program and consider them an integral part of the product.
Third-party libraries
If your application uses third-part vendor libraries, you should consider whether the linking is static or dynamic (if it is a DLL), and whether the libaries are upward-compatible. If you statically link a library with your application, you can use either the ++MOD method or the ++PROGRAM method, as described in Linking.