The exits must follow standard linkage conventions. They must save the registers on entry and restore the registers when they return.

The SEND, OPERATOR SEND, and LISTBC exits must be reentrant, refreshable, and reusable. The SEND and LISTBC exits are APF-authorized. The OPERATOR SEND exits are not APF-authorized, however, they execute in supervisor state with a key of 0.

The user SEND and the LISTBC exits can use any of the TSO/E service routines. For a description of the service routines, see .

If one of the exits obtains a system resource, you must write a termination exit to free the resource before the command or subcommand processor completes its processing.