Exit IXZXIT01 receives control under the same task that issues the IXZXIXSM or IXZXIXAC macro. This exit receives control after a message packet has been created but before that packet is sent to its target member (specified by the IXZXIXSM macro) and when the acknowledging member replies to the originating system for all acknowledgements (REQTYPE= SYNC | ASYNC | ASYNCACK). Although REQTYPE=COMM messages are also acknowledged to JES XCF, exit IXZXIT01 is not called for that purpose.

The data passed to this exit is in a data space; therefore, the data can be accessed through an AR/GPR pair. The exit receives control in access register address space control (AR ASC) mode. AR1 contains the ALET of the data space containing the exit parameter list (mapped by IXZ$XPL) passed to the exit; GPR1 contains the address of IXZ$XPL within the data space.

The path from the exit caller to the message data includes the following links as shown in Figure 1:

1. An installation exit or JES sends (through macro IXZXIXSM) or acknowledges (through macro IXZXIXAC) a message
2. When JES XCF invokes IXZXIT01 in the JES XCF address space, AR1 contains the ALET of the data space containing the parameter list, and GPR1 contains the address of the parameter list within the address space
3. Mapping IXZ$XPL contains data common to all of the exits, associated exit-specific data, and a pointer to the message data.

Figure 1. Access path from exit caller to message data