IBM SC33-1683-02 - Manual (Page 35)

Chapter 1. Global user exit programs
This chapter describes the CICS global user exit points, and how you can use
them, in conjunction with programs of a special type that you write yourself (global
user exit programs), to customize your CICS system. The chapter is divided into
the following sections:
1. “Overview — what is a global user exit?” is an introduction to global user
exits, describing their main features and what they can be used for.
2. “Global user exit programs” on page 4 covers topics that you need to
consider when writing a global user exit program. It deals with the following:
v “Register conventions” on page 4
v “31-bit addressing implications” on page 5
v “Using CICS services” on page 5
v “Using EDF with global user exits” on page 6
v “The global work area” on page 6
v “Making trace entries” on page 7
v “Parameters passed to the global user exit program” on page 7
v “Returning values to CICS” on page 10
v “Restrictions on the use of fields as programming interfaces” on page 11
v “Exit programs and the CICS storage protection facility” on page 11
v “Errors in user exit programs” on page 12
v “Defining, enabling, and disabling an exit program” on page 13
v “Invoking more than one exit program at a single exit” on page 13
v “Invoking a single exit program at more than one exit” on page 14
v “Sample global user exit programs” on page 14.
3. “List of global user exit points” on page 19 lists the global user exit points in
alphabetical order. The sections that follow contain detailed information about
each global user exit point, including the place in the CICS code at which it
occurs, and the specific (as distinct from the standard) parameters that are
passed to an exit program.
Overview — what is a global user exit?
A global user exit point (sometimes referred to simply as a “global user exit”) is a
place in a CICS module or domain 1 at which CICS can transfer control to a
program that you have written (a global user exit program), and at which CICS can
resume control when your exit program has finished its work. You do not have to
use any of the global user exits, but you can use them to extend and customize the
function of your CICS system according to your own requirements. For a complete
list of the global user exit points, see Table 2 on page 19.
1. A domain is an isolated functional unit of CICS Transaction Server for OS/390 Release 3 that communicates with the rest of CICS
and with other programs using a set of strictly defined and controlled interfaces.
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