Usage notes

  1. You can use both the MQPUT and MQPUT1 calls to put messages on a queue; which call to use depends on the circumstances:
  2. If an application puts a sequence of messages on the same queue without using message groups, the order of those messages is preserved provided that the conditions detailed below are satisfied. Some conditions apply to both local and remote destination queues; other conditions apply only to remote destination queues.

    Conditions that apply to local and remote destination queues

    Additional conditions that apply to remote destination queues

    If these conditions are not satisfied, you can use message groups to preserve message order, but this requires both the sending and receiving applications to use the message-grouping support. For more information about message groups, see:

  3. The following notes apply to the use of distribution lists.

    Distribution lists are supported in the following environments: AIX, HP-UX, i5/OS, Solaris, Linux, Windows, plus WebSphere MQ clients connected to these systems.

    1. You can put messages to a distribution list using either a version-1 or a version-2 MQPMO. If you use a version-1 MQPMO (or a version-2 MQPMO with RecsPresent equal to zero), the application can provide no put message records or response records. You cannot identify the queues that encounter errors if the message is sent successfully to some queues in the distribution list and not others.

      If the application provides put message records or response records, set the Version field to MQPMO_VERSION_2.

      You can also use a version-2 MQPMO to send messages to a single queue that is not in a distribution list, by ensuring that RecsPresent is zero.

    2. The completion code and reason code parameters are set as follows:
      • If the puts to the queues in the distribution list all succeed or fail in the same way, the completion code and reason code parameters are set to describe the common result. The MQRR response records (if provided by the application) are not set in this case.

        For example, if every put succeeds, the completion code and reason code are set to MQCC_OK and MQRC_NONE; if every put fails because all the queues are inhibited for puts, the parameters are set to MQCC_FAILED and MQRC_PUT_INHIBITED.

      • If the puts to the queues in the distribution list do not all succeed or fail in the same way:
        • The completion code parameter is set to MQCC_WARNING if at least one put succeeded, and to MQCC_FAILED if all failed.
        • The reason code parameter is set to MQRC_MULTIPLE_REASONS.
        • The response records (if provided by the application) are set to the individual completion codes and reason codes for the queues in the distribution list.

        If the put to a destination fails because the open for that destination failed, the fields in the response record are set to MQCC_FAILED and MQRC_OPEN_FAILED; that destination is included in InvalidDestCount.

    3. If a destination in the distribution list resolves to a local queue, the message is placed on that queue in normal form (that is, not as a distribution-list message). If more than one destination resolves to the same local queue, one message is placed on the queue for each such destination.

      If a destination in the distribution list resolves to a remote queue, a message is placed on the appropriate transmission queue. Where several destinations resolve to the same transmission queue, a single distribution-list message containing those destinations can be placed on the transmission queue, even if those destinations were not adjacent in the list of destinations provided by the application. However, this can be done only if the transmission queue supports distribution-list messages (see DistLists).

      If the transmission queue does not support distribution lists, one copy of the message in normal form is placed on the transmission queue for each destination that uses that transmission queue.

      If a distribution list with the application message data is too big for a transmission queue, the distribution list message is split into smaller distribution-list messages, each containing fewer destinations. If the application message data only just fits on the queue, distribution-list messages cannot be used at all, and the queue manager generates one copy of the message in normal form for each destination that uses that transmission queue.

      If different destinations have different message priority or message persistence (this can occur when the application specifies MQPRI_PRIORITY_AS_Q_DEF or MQPER_PERSISTENCE_AS_Q_DEF), the messages are not held in the same distribution-list message. Instead, the queue manager generates as many distribution-list messages as are necessary to accommodate the differing priority and persistence values.

    4. A put to a distribution list can result in:
      • A single distribution-list message, or
      • A number of smaller distribution-list messages, or
      • A mixture of distribution list messages and normal messages, or
      • Normal messages only.
      Which of the above occurs depends on whether:
      • The destinations in the list are local, remote, or a mixture.
      • The destinations have the same message priority and message persistence.
      • The transmission queues can hold distribution-list messages.
      • The transmission queues' maximum message lengths are large enough to accommodate the message in distribution-list form.
      However, regardless of which of the above occurs, each physical message resulting (that is, each normal message or distribution-list message resulting from the put) counts as only one message when:
      • Checking whether the application has exceeded the permitted maximum number of messages in a unit of work (see the MaxUncommittedMsgs queue-manager attribute).
      • Checking whether the triggering conditions are satisfied.
      • Incrementing queue depths and checking whether the queues' maximum queue depth would be exceeded.
    5. Any change to the queue definitions that would have caused a handle to become invalid had the queues been opened individually (for example, a change in the resolution path), does not cause the distribution-list handle to become invalid. However, it does result in a failure for that particular queue when the distribution-list handle is used on a subsequent MQPUT call.
  4. If a message is put with one or more MQ header structures at the beginning of the application message data, the queue manager performs certain checks on the header structures to verify that they are valid. If the queue manager detects an error, the call fails with an appropriate reason code. The checks performed vary according to the particular structures that are present:

    General checks performed by the queue manager include the following:

    In addition to general checks on structures, the following conditions must be satisfied:

  5. For the Visual Basic programming language, the following points apply: