Cluster workload balancing - channel attributes

An alphabetical list of the channel attributes used in cluster workload balancing.

CLWLPRTY (Cluster workload priority)

The CLWLPRTY channel attribute specifies the priority order for channels for cluster workload distribution. The value must be in the range 0-9, where 0 is the lowest priority and 9 is the highest.

Use the CLWLPRTY channel attribute to set a priority order for the available cluster destinations. IBM® MQ selects the destinations with the highest priority before selecting destinations with the lowest cluster destination priority. If there are multiple destinations with the same priority, it selects the least recently used destination.

If there are two possible destinations, you can use this attribute to allow failover. Messages go to the queue manager with the highest priority channel. If it becomes unavailable then messages go to the next highest priority queue manager. Lower priority queue managers act as reserves.

IBM MQ checks channel status before prioritizing the channels. Only available queue managers are candidates for selection.

Notes:
  • Specify this attribute on the cluster-receiver channel at the target queue manager. Any balancing you specify on the matching cluster-sender channel is likely to be ignored. See Cluster channels.
  • The availability of a remote queue manager is based on the status of the channel to that queue manager. When channels start, their state changes several times, with some of the states being less preferential to the cluster workload management algorithm. In practice this means that lower priority (backup) destinations can be chosen while the channels to higher priority (primary) destinations are starting.
  • If you need to ensure that no messages go to a backup destination, do not use CLWLPRTY. Consider using separate queues, or CLWLRANK with a manual switch over from the primary to back up.

CLWLRANK (Cluster workload rank)

The CLWLRANK channel attribute specifies the rank of channels for cluster workload distribution. The value must be in the range 0-9, where 0 is the lowest rank and 9 is the highest.

Use the CLWLRANK channel attribute if you want control over the final destination for messages sent to a queue manager in another cluster. Control the choice of final destination by setting the rank of the channels connecting a queue manager to the gateway queue managers at the intersection of the clusters.

When you set CLWLRANK, messages take a specified route through the interconnected clusters towards a higher ranked destination. For example, messages arrive at a gateway queue manager that can send them to either of two queue managers using channels ranked 1 and 2. They are automatically sent to the queue manager connected by a channel with the highest rank, in this case the channel to the queue manager ranked 2.

IBM MQ gets the rank of channels before checking channel status. Getting the rank before checking channel status means that even non-accessible channels are available for selection. It allows messages to be routed through the network even if the final destination is unavailable.

Notes:
  • Specify this attribute on the cluster-receiver channel at the target queue manager. Any balancing you specify on the matching cluster-sender channel is likely to be ignored. See Cluster channels.
  • If you also used the priority attribute CLWLPRTY, IBM MQ selects between available destinations. If a channel is not available to the destination with the highest rank, the message is held on the transmission queue. It is released when the channel becomes available. The message does not get sent to the next available destination in the rank order.

CLWLWGHT (Cluster workload weight)

The CLWLWGHT channel attribute specifies the weight applied to CLUSSDR and CLUSRCVR channels for cluster workload distribution. The value must be in the range 1-99, where 1 is the lowest weight and 99 is the highest.

Use CLWLWGHT to send servers with more processing power more messages. The higher the channel weight, the more messages are sent over that channel.

Notes:
  • Specify this attribute on the cluster-receiver channel at the target queue manager. Any balancing you specify on the matching cluster-sender channel is likely to be ignored. See Cluster channels.
  • When CLWLWGHT is modified from the default of 50 on any channel, workload balancing becomes dependent on the total number of times each channel was chosen for a message sent to any clustered queue. For more information, see The cluster workload management algorithm.

NETPRTY (Network-connection priority)

The NETPRTY channel attribute specifies the priority for a CLUSRCVR channel. The value must be in the range 0-9, where 0 is the lowest priority and 9 is the highest.

Use the NETPRTY attribute to make one network the primary network, and another network the backup network. Given a set of equally ranked channels, clustering chooses the path with the highest priority when multiple paths are available.

A typical example of using the NETPRTY channel attribute is to differentiate between networks that have different costs or speeds and connect the same destinations.

Note: Specify this attribute on the cluster-receiver channel at the target queue manager. Any balancing you specify on the matching cluster-sender channel is likely to be ignored. See Cluster channels.