Usage notes

  1. The queue manager to which connection is made using the MQCONN call is called the local queue manager.
  2. Queues that are owned by the local queue manager appear to the application as local queues. It is possible to put messages on and get messages from these queues.

    Shared queues that are owned by the queue-sharing group to which the local queue manager belongs appear to the application as local queues. It is possible to put messages on and get messages from these queues.

    Queues that are owned by remote queue managers appear as remote queues. It is possible to put messages on these queues, but not to get messages from these queues.

  3. If the queue manager fails while an application is running, the application must issue the MQCONN call again to obtain a new connection handle to use on subsequent MQ calls. The application can issue the MQCONN call periodically until the call succeeds.

    If an application is not sure whether it is connected to the queue manager, the application can safely issue an MQCONN call to obtain a connection handle. If the application is already connected, the handle returned is the same as that returned by the previous MQCONN call, but with completion code MQCC_WARNING and reason code MQRC_ALREADY_CONNECTED.

  4. When the application has finished using MQ calls, the application must use the MQDISC call to disconnect from the queue manager.
  5. On z/OS:
  6. On z/OS, to define the available queue managers:

    For more information on using these macros, see the WebSphere MQ for z/OS System Setup Guide.

  7. On i5/OS, applications written for previous releases of the queue manager can run without recompiling. This is called compatibility mode. This mode of operation provides a compatible run-time environment for applications. It comprises the following:

    These three interfaces do not include capabilities that were introduced in MQSeries(R) Version 5.1. For example, the MQBACK, MQCMIT, and MQCONNX calls are not supported. The support provided by these interfaces is for single-threaded applications only.

    Support for the new MQ calls in single-threaded applications, and for all MQ calls in multi-threaded applications, is provided through the service programs LIBMQM and LIBMQM_R.

  8. On i5/OS, programs that end abnormally are not automatically disconnected from the queue manager. Write applications to allow for the possibility of the MQCONN or MQCONNX call returning completion code MQCC_WARNING and reason code MQRC_ALREADY_CONNECTED. Use the connection handle returned in this situation as normal.