APAR status
Closed as program error.
Error description
When using a uniform cluster, a large number of status messages are being sent through cluster channels although no re-connectable clients are present. These are internal MQPCF status messages which bounce between queue managers as a result of them believing that their system topics, are no longer a local TOPICHOST. The problem can also impact the ability for applications to be re-balanced correctly Use runmqsc to display the topic status and check the CLROUTE and PUBCOUNT - DIS TPSTATUS ('$SYS/MQ/INTERQM/BROADCAST') TYPE(TOPIC)
Local fix
Problem summary
**************************************************************** USERS AFFECTED: Users of Uniform Cluster configurations. Platforms affected: MultiPlatform **************************************************************** PROBLEM DESCRIPTION: When a queue manager starts, it will restore locally defined topic objects to the topic tree. After the topic tree has been initialized with defined topics, it can be updated with entries from the cluster cache. During cache restoration, updates to in the topic tree are made but this should not include topics which had previously been marked as 'DELETED' as this can modify the internal flags for topics which are defined locally. If the topic being updated is defined with CLROUTE(TOPICHOST) set, the internal flags were incorrectly updated, removing the local flag. Messages published to the TOPICSTR of the topic, would attempt to find an alternative TOPICHOST elsewhere in the cluster configuration, excluding the locally defined topic. If all TOPICHOST's (for a given topic string) were in this confused state, messages would continually flow from one queue manager to another attempting to find a suitable host which was considered to be locally defined. This appeared as though a vast quantity of messages are flowing through the cluster. With respect to Uniform Clusters, there are system topics which are defined with CLROUTE(TOPICHOST) that can cause the issue when they are deleted from the cluster. These topics can be marked as deleted from the cluster as a result of - issuing REFRESH CLUSTER(<uniform cluster name>) - removing the queue manager from the Uniform Cluster (and subsequently re-introducing back into the cluster)
Problem conclusion
The problem is resolved by preventing deleted topics from updating the topic tree during cache restore operations. The restore operations can result from : 	- After restarting the Queue Manager. 	- After enabling the SYSTEM.CLUSTER.COMMAND.QUEUE for MQGET operations. --------------------------------------------------------------- The fix is targeted for delivery in the following PTFs: Version Maintenance Level v9.1 LTS 9.1.0.9 v9.2 LTS 9.2.0.4 v9.x CD 9.2.4 The latest available maintenance can be obtained from 'WebSphere MQ Recommended Fixes' http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037 If the maintenance level is not yet available information on its planned availability can be found in 'WebSphere MQ Planned Maintenance Release Dates' http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309 ---------------------------------------------------------------
Temporary fix
Comments
APAR Information
APAR number
IT36110
Reported component name
MQ BASE V9.2
Reported component ID
5724H7281
Reported release
920
Status
CLOSED PER
PE
NoPE
HIPER
YesHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2021-03-04
Closed date
2021-08-10
Last modified date
2021-08-10
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Fix information
Fixed component name
MQ BASE V9.2
Fixed component ID
5724H7281
Applicable component levels
[{"Line of Business":{"code":"LOB45","label":"Automation"},"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSYHRD","label":"IBM MQ"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"920"}]
Document Information
Modified date:
11 August 2021