gtpi1m3xSystem Installation Support Reference

Message Queue Interface (MQI) Channel Exits

Standard MQI client support comes with 3 user exits that allow you to customize the channel interface. These exits are referred to as message channel agent (MCA) exit routines in the MQSeries publications. These exits are optional and only called if they have been defined in the MQI channel directory using the ZMQID DEFINE or ZMQID ALTER command. The MCA exits are:

Security
Normally, security exits work in pairs, one at both the client and server ends of the channel. This exit is provided to give the customer the ability to check authorization to start the channel connection. The security exit is called when the MQI channel is first started.

Receive
The receive exit is called after each message segment is received from the server.

Send
The send exit is called just before a message segment is transmitted on the server.

Programming Considerations

  1. The interface for the MCA exits are specified in the cmqxc.h header file. The user exit code will be given control using the standard ISO-C DLM enter.
  2. If an irrecoverable error occurs, the MCA user exits can SERRC with exit. Otherwise, the user exits should always return to the MQI client support code, only manipulating the data passed in the documented interface.
  3. Any fields used in the ECB should be restored to their original values before returning to the MQI client support code.
Note:
For a detailed description on how the MCA exits work, see the MQSeries Distributed Queue Management Guide. For more information about defining or changing MQI channel definition exit attributes see the ZMQID DEFINE and ZMQID ALTER command descriptions in TPF Operations.