This section describes the exit you can use to add your own CLIST statements.

The CLIST language provides statements that let you structure your programs, perform I/O, define and modify variables, and monitor the conditions under which CLISTs execute. , describes the CLIST statements that are supplied by TSO/E. In addition to these statements, TSO/E provides an exit that you can use to add your own CLIST statements.

Processing for a CLIST is done in two steps: phase 1, which is performed by the EXEC command processor, and phase 2. In phase 1, the EXEC command processor reads the CLIST records from the input data set and builds an in-storage command procedure. EXEC then places the command procedure that it built on the input stack. This stack is maintained by TSO/E to determine the source of input. Phase 2 processing receives control as each record is removed from the stack. The CLIST statement exit receives control during phase 2 processing.

You can use the CLIST statement exit as a fast path for executing TSO/E commands from a CLIST. To avoid the overhead that normally occurs when TSO/E commands are executed from a CLIST, your exit can treat TSO/E commands as installation-written statements. Your exit can directly invoke a TSO/E command processor, using the ATTACH or LINK macro instruction. Depending upon whether the TSO/E command completed successfully, your exit must set the appropriate return code to indicate that an installation-written CLIST statement was processed.