Distributed publish/subscribe system queues

Four system queues are used by queue managers for publish/subscribe messaging. You need to be aware of their existence only for problem determination and capacity planning purposes.

See Balancing producers and consumers in publish/subscribe networks for guidance on how to monitor these queues.

Table 1. Publish/subscribe system queues on Multiplatforms
System queue	Purpose
SYSTEM.INTER.QMGR.CONTROL	IBM MQ distributed publish/subscribe control queue
SYSTEM.INTER.QMGR.FANREQ	IBM MQ distributed publish/subscribe internal proxy subscription fan-out process input queue
SYSTEM.INTER.QMGR.PUBS	IBM MQ distributed publish/subscribe publications
SYSTEM.HIERARCHY.STATE	IBM MQ distributed publish/subscribe hierarchy relationship state

On z/OS®, you set up the necessary system objects when you create the queue manager, by including the CSQ4INSX, CSQ4INSR and CSQ4INSG samples in the CSQINP2 initialization input data set. For more information, see Task 13: Customize the initialization input data sets.

The attributes of the publish/subscribe system queues are shown in Table 2.

Table 2. Attributes of publish/subscribe system queues
Attribute	Default value
DEFPSIST	Yes
DEFSOPT	EXC
MAXMSGL	On Multiplatforms: The value of the MAXMSGL parameter of the ALTER QMGR command On z/OS: 104857600 (that is, 100 MB)
MAXDEPTH	999999999
SHARE	N/A
STGCLASS	This attribute is used only on z/OS platforms

Note: The only queue that contains messages put by applications is SYSTEM.INTER.QMGR.PUBS. MAXDEPTH is set to its maximum value for this queue to allow temporary build up of published messages during outages or times of excessive load. If the queue manager is running on a system where that depth of queue could not be contained, this should be adjusted.