Channel-exit calls and data structures

This collection of topics provide reference information about the special IBM MQ calls and data structures that we can use when you write channel exit programs.

This information is product-sensitive programming interface information. We can write IBM MQ user exits in the following programming languages:

We can also write user exits in Java for use only with Java and JMS applications. For more information about creating and using channel exits with the IBM MQ classes for Java, see Use channel exits in IBM MQ classes for Java and for IBM MQ classes for JMS, see Use channel exits with IBM MQ classes for JMS.

We cannot write IBM MQ user exits in TAL or Visual Basic. However, a declaration for the MQCD structure is provided in Visual Basic for use on the MQCONNX call from an IBM MQ MQI client program.

In a number of cases in the descriptions that follow, parameters are arrays or character strings with a size that is not fixed. For these parameters, a lowercase n is used to represent a numeric constant. When the declaration for that parameter is coded, the n must be replaced by the numeric value required. For further information about the conventions used in these descriptions, see the Elementary data types.

Data definition files

Data definition files are supplied with IBM MQ for each of the supported programming languages. For details of these files, see Copy, header, include, and module files.

• MQ_CHANNEL_EXIT - Channel exit
  The MQ_CHANNEL_EXIT call describes the parameters that are passed to each of the channel exits called by the Message Channel Agent.
• MQ_CHANNEL_AUTO_DEF_EXIT - Channel auto-definition exit
  The MQ_CHANNEL_AUTO_DEF_EXIT call describes the parameters that are passed to the channel auto-definition exit called by the Message Channel Agent.
• MQXWAIT - Wait in exit
  The MQXWAIT call waits for an event to occur. It can be used only from a channel exit on z/OS.
• MQCD - Channel definition
  The MQCD structure contains the parameters which control execution of a channel. It is passed to each channel exit that is called from a Message Channel Agent (MCA).
• MQCXP - Channel exit parameter
  The MQCXP structure is passed to each type of exit called by a Message Channel Agent (MCA), client-connection channel, or server-connection channel.
• MQXWD - Exit wait descriptor
  The MQXWD structure is an input/output parameter on the MQXWAIT call.

Parent topic: User exits, API exits, and installable services reference