Intra-group queuing

Intra-group queuing allows transfer of messages between queue managers in a queue sharing group.

We can perform fast message transfer between queue managers in a queue sharing group without defining channels. This uses a system queue called the SYSTEM.QSG.TRANSMIT.QUEUE, which is a shared transmission queue. Each queue manager in the queue sharing group starts a task called the intra-group queuing agent, which waits for messages to arrive on this queue that are destined for their queue manager. When such a message is detected, it is removed from the queue and placed on the correct destination queue.

Standard name resolution rules are used but, if intra-group queuing (IGQ) is enabled and the target queue manager is within the queue sharing group, the SYSTEM.QSG.TRANSMIT.QUEUE is used to transfer the message to the correct destination queue manager instead of using a transmission queue and channel.

You enable intra-group queuing through a queue manager attribute. Intra-group queuing moves nonpersistent messages outside sync point, and persistent messages within sync point. If it finds a problem delivering messages to the target queue, intra-group queuing tries to put them to the dead-letter queue. If the dead-letter queue is full or undefined, nonpersistent messages are discarded, but persistent messages are backed out and returned to the SYSTEM.QSG.TRANSMIT.QUEUE, and the IGQ agent tries to deliver the messages until it is successful.

An inbound shared channel that receives a message destined for a queue on a different queue manager in the queue sharing group can use intra-group queuing to hop the message to the correct destination.

There might be times when we want the local queue manager to put a message directly to the target queue if the target queue is a shared queue, rather than the message first being transferred to the target queue manager. We can use the queue manager attribute SQQMNAME to control this. If you set the value of SQQMNAME to USE, the MQOPEN command is performed on the queue manager specified by the ObjectQMgrName. However, if the target queue is a shared queue and you set the value of SQQMNAME to IGNORE, and the ObjectQMgrName is that of another queue manager in the queue sharing group, the shared queue is opened on the local queue manager. If the local queue manager cannot open the target queue, or put a message to the queue, the message is transferred to the specified ObjectQMgrName through either IGQ or an MQ channel.

Intra-group queuing (IGQ) supports large messages, the largest being 100 MB minus the length of the transmission queue header.

If we use this feature, users must have the same access to the queues on each queue manager in the queue sharing group.

Parent topic: Distributed queuing and queue sharing groups