Description

The IXCMSGIX macro is the interface to the XCF (cross-system coupling facility) message-in service. This interface is the successor to the IXCMSGI macro interface, contains all the functionality of the IXCMSGI message-in macro interface and is the suggested XCF message-in service interface to use.

The IXCMSGIX macro allows a member of an XCF group to receive a message or response from another member in its XCF group. IXCMSGIX, and its companion services, IXCMSGOX (message-out service) and IXCMSGC (message control service), comprise the XCF signalling services. To receive messages and responses through XCF signalling services, you must write either a message user routine or a message notify user routine that invokes the IXCMSGIX macro. When an XCF member sends a message or response by issuing the IXCMSGOX macro, XCF schedules either the message user routine or the message notify user routine belonging to the member receiving the message.

Messages can vary in length up to 128M bytes. A “large message” is defined to be one that is greater than 62464 (61K) bytes. XCF handles large messages somewhat differently from messages of less than 61K bytes, and also imposes the following restrictions when sending large messages:

Both the sending and the target systems must be running OS/390® Release 8 or higher. (This does not necessarily imply that all members residing on those systems support large message delivery.)
Both the sending and the target members must have specified when they joined the XCF group that they supported large message delivery. (Each must have specified GT61KMSG=YES on the IXCJOIN invocation.)

Members of an XCF group can receive message data using either a single buffer or multiple buffers.

Be sure to read the IXCMSGIX guidance information in z/OS MVS Programming: Sysplex Services Guide. The information presented here assumes you have done so. IXCMSGIX guidance information includes:

Illustrations showing the message data element formats specified by the various IXCMSGIX parameters.
Information on designing a protocol for sending and receiving multipart messages.
Information on writing a message user routine and a message notify user routine.