Queue definition commands

Cluster attributes that can be specified on the queue definition commands.

The DEFINE QLOCAL, DEFINE QREMOTE, and DEFINE QALIAS commands

The cluster attributes on the DEFINE QLOCAL, DEFINE QREMOTE, and DEFINE QALIAS commands, and the three equivalent ALTER commands, are:

CLUSTER

Specifies the name of the cluster to which the queue belongs.

CLUSNL

Specifies a namelist of cluster names.

DEFBIND

Specifies the binding to be used when an application specifies MQOO_BIND_AS_Q_DEF on the MQOPEN call. The options for this attribute are:

• Specify DEFBIND(OPEN) to bind the queue handle to a specific instance of the cluster queue when the queue is opened. DEFBIND(OPEN) is the default for this attribute.
• Specify DEFBIND(NOTFIXED) so that the queue handle is not bound to any instance of the cluster queue.
• Specify DEFBIND(GROUP) to allow an application to request that a group of messages are all allocated to the same destination instance.

When multiple queues with the same name are advertised in a Queue Manager Cluster, applications can choose whether to send all messages from this application to a single instance (MQOO_BIND_ON_OPEN), to allow the workload management algorithm to select the most suitable destination on a per message basis (MQOO_BIND_NOT_FIXED), or allow an application to request that a 'group' of messages be all allocated to the same destination instance (MQOO_BIND_ON_GROUP). The workload balancing is re-driven between groups of messages (without requiring an MQCLOSE and MQOPEN of the queue).

When you specify DEFBIND on a queue definition, the queue is defined with one of the attributes, MQBND_BIND_ON_OPEN, MQBND_BIND_NOT_FIXED, or MQBND_BIND_ON_GROUP. Either MQBND_BIND_ON_OPEN or MQBND_BIND_ON_GROUP must be specified when using groups with clusters.

We recommend that you set the DEFBIND attribute to the same value on all instances of the same cluster queue. Because MQOO_BIND_ON_GROUP is new in IBM® WebSphere MQ Version 7.1, it must not be used if any of the applications opening this queue are connecting to IBM WebSphere MQ Version 7.0.1 or earlier queue managers.

CLWLRANK

Applies a ranking factor to a queue for workload management purposes. CLWLRANK parameter is not supported on model queues. The cluster workload algorithm selects a destination queue with the highest rank. By default CLWLRANK for all queues is set to zero.

If the final destination is a queue manager on a different cluster, we can set the rank of any intermediate gateway queue managers at the intersection of neighboring clusters. With the intermediate queue managers ranked, the cluster workload algorithm correctly selects a destination queue manager nearer the final destination.

The same logic applies to alias queues. The rank selection is made before the channel status is checked, and therefore even non-accessible queue managers are available for selection. This has the effect of allowing a message to be routed through a network, rather than having it select between two possible destinations (as the priority would). So, if a channel is not started to the place where the rank has indicated, the message is not routed to the next highest rank, but waits until a channel is available to that destination (the message is held on the transmit queue).

CLWLPRTY

Applies a priority factor to a queue for workload management purposes. The cluster workload algorithm selects a destination queue with the highest priority. By default priority for all queues is set to zero.

If there are two possible destination queues, we can use this attribute to make one destination failover to the other destination. The priority selection is made after the channel status is checked. All messages are sent to the queue with the highest priority unless the status of the channel to that destination is not as favorable as the status of channels to other destinations. This means that only the most accessible destinations are available for selection. This has the effect of prioritizing between multiple destinations that are all available.

CLWLUSEQ

Specifies the behavior of an MQPUT operation for a queue. This parameter specifies the behavior of an MQPUT operation when the target queue has a local instance and at least one remote cluster instance (except where the MQPUT originates from a cluster channel). This parameter is only valid for local queues.

Possible values are: QMGR (the behavior is as specified by the CLWLUSEQ parameter of the queue manager definition), ANY (the queue manager treats the local queue as another instance of the cluster queue, for the purposes of workload distribution), LOCAL (the local queue is the only target of the MQPUT operation, providing the local queue is put enabled). The MQPUT behavior depends upon the cluster workload management algorithm.

The DISPLAY QUEUE and DISPLAY QCLUSTER commands

The attributes on the DEFINE QLOCAL, DEFINE QREMOTE, and DEFINE QALIAS commands also apply to the DISPLAY QUEUE command.

To display information about cluster queues, specify a queue type of QCLUSTER or the keyword CLUSINFO on the DISPLAY QUEUE command, or use the command DISPLAY QCLUSTER.

The DISPLAY QUEUE or DISPLAY QCLUSTER command returns the name of the queue manager that hosts the queue (or the names of all queue managers if there is more than one instance of the queue). It also returns the system name for each queue manager that hosts the queue, the queue type represented, and the date and time at which the definition became available to the local queue manager. This information is returned using the CLUSQMGR, QMID, CLUSQT, CLUSDATE, and CLUSTIME attributes.

The system name for the queue manager ( QMID ), is a unique, system-generated name for the queue manager.

We can define a cluster queue that is also a shared queue. For example. on z/OS® we can define:

DEFINE QLOCAL(MYQUEUE) CLUSTER(MYCLUSTER) QSGDISP(SHARED) CFSTRUCT(STRUCTURE)

The equivalent PCFs are MQCMD_CHANGE_Q, MQCMD_COPY_Q, MQCMD_CREATE_Q, and MQCMD_INQUIRE_Q.