The Set sample programs

The Set sample programs inhibit put operations on a queue by using the MQSET call to change the queue's InhibitPut attribute. See Features demonstrated in the sample programs for the names of these programs.

The programs are intended to run as triggered programs, so their only input is an MQTMC2 (trigger message) structure that contains the name of a target queue whose attributes are to be inquired. The C version also uses the queue manager name. The COBOL version uses the default queue manager.

For the triggering process to work, you must ensure that the Set sample program you want to use is triggered by messages arriving on queue SYSTEM.SAMPLE.SET. To do this, specify the name of the Set sample program you want to use in the ApplicId field of the process definition SYSTEM.SAMPLE.SETPROCESS. The sample queue has a trigger type of FIRST; if there are already messages on the queue before you run the Request sample, the Set sample is not triggered by the messages you send.

When you have set the definition correctly:

• For OS/2, UNIX systems, Compaq OpenVMS Alpha, and Windows systems, start the runmqtrm program in one session, then start the amqsreq program in another.
• For OS/400, start the AMQSERV4 program in one session, then start the AMQSREQ4 program in another. You could use AMQSTRG4 instead of AMQSERV4, but potential job submission delays could make it less easy to follow what is happening.

Use the Request sample programs to send request messages, each containing just a queue name, to queue SYSTEM.SAMPLE.SET. For each request message, the Set sample programs send a reply message containing a confirmation that put operations have been inhibited on the specified queue. The replies are sent to the reply-to queue specified in the request message.

Design of the Set sample program

The program opens the queue named in the trigger message structure it was passed when it started. (For clarity, we will call this the request queue.) The program uses the MQOPEN call to open this queue for shared input.

The program uses the MQGET call to remove messages from this queue. This call uses the MQGMO_ACCEPT_TRUNCATED_MSG and MQGMO_WAIT options, with a wait interval of 5 seconds. The program tests the descriptor of each message to see if it is a request message; if it is not, the program discards the message and displays a warning message.

For each request message removed from the request queue, the program reads the name of the queue (which we will call the target queue) contained in the data and opens that queue using the MQOPEN call with the MQOO_SET option. The program then uses the MQSET call to set the value of the InhibitPut attribute of the target queue to MQQA_PUT_INHIBITED.

If the MQSET call is successful, the program uses the MQPUT1 call to put a reply message on the reply-to queue. This message contains the string PUT inhibited.

If the MQOPEN or MQSET call is unsuccessful, the program uses the MQPUT1 call to put a report message on the reply-to queue. In the Feedback field of the message descriptor of this report message is the reason code returned by either the MQOPEN or MQSET call, depending on which one failed.

After the MQSET call, the program closes the target queue using the MQCLOSE call.

When there are no messages remaining on the request queue, the program closes that queue and disconnects from the queue manager.