Enable GROUP units of recovery

A queue sharing group can configure and enable support for GROUP units of recovery.

To use GROUP units of recovery on a queue manager within a QSG, enable the GROUPUR queue manager attribute. For more information about this concept, see Unit of recovery disposition on z/OS before reading the rest of this topic.

When the GROUPUR queue manager attribute is enabled, the queue manager accepts new connections with a GROUP unit of recovery disposition. If you disable this attribute new connections with this disposition are not accepted, although applications already connected is unaffected until they disconnect.

When an application connects with a GROUP unit of recovery disposition and either inquires what transactions are in doubt or attempts to resolve a transaction that was started elsewhere in the queue sharing group (QSG), the queue manager to which it is now connected must be able to communicate with the other members of the queue sharing group so that it can process the request. To do this it uses a shared queue called SYSTEM.QSG.UR.RESOLUTION.QUEUE. This queue must be on a recoverable application structure called CSQSYSAPPL. The structure must be recoverable because persistent messages are stored on this queue when processing resolution requests.

Before we can enable GROUP units of recovery, we must ensure that the coupling facility structure and the shared queue are defined. We can use the definitions in the CSQ4INSS sample. When the queue is defined, or detected during startup, each queue manager in the queue sharing group opens the queue so that it can receive incoming requests. To delete or move the queue because it has been defined incorrectly we can request that the queue managers close their open handles on it by updating the queue object to inhibit MQGET requests. When you have made the necessary corrections, permitting applications to get messages from the queue once more directs each queue manager to reopen it. Use the DISPLAY QSTATUS command to identify what handles are open on a queue.

When you have completed this setup we can then enable GROUP units of recovery on each queue manager that we want transactional applications to be able to connect to with a GROUP unit of recovery disposition. This need not be all of the queue managers within the queue sharing group but if you choose to only enable this functionality on a subset of the queue sharing group we must ensure that your applications only attempt to connect to queue managers on which you have enabled it. For more information, see Application support.

• It belongs to a queue sharing group.
• The shared-queue called SYSTEM.QSG.UR.RESOLUTION.QUEUE has been defined, according to the the definition in CSQ4INSS.
• The SYSTEM.QSG.UR.RESOLUTION.QUEUE is on a recoverable CF structure called CSQSYSAPPL.

If any of the above checks fail, the GROUPUR attribute remains disabled and a message code is returned.

These configuration checks are also performed at queue manager startup if the queue manager attribute is enabled. If any of the checks fail during startup GROUP units of recovery is disabled and the queue manager issues a message identifying which check failed. When you have performed the necessary corrective action we must then re-enable the queue manager attribute.