The JES2 exit facility allows you to define and use your own exits, should the IBM-defined exits not suffice. Exits created by users as modifications to JES2 and are called installation-defined exits. You can define exits by placing an exit point at appropriate points in the JES2 code, or in your own exit routine code. IBM-defined exit points are established in the same manner, but the exit point is placed appropriately for the specific function for which it is intended. Note, however, that implementing your own exit can be considerably more difficult than writing an exit routine for an IBM-defined exit. See z/OS JES2 Installation Exits for explanations of JES2 coding conventions, restrictions and how JES2 exits are packaged. See z/OS JES2 Macros for the JES2 macros that are available and intended for your use.