APAR status
Closed as program error.
Error description
An application connecting as a client (eg. over TCP/IP) uses "asynchronous consumer" APIs MQCB and MQCTL. After a while, the queue manager entered a state where it stopped delivering messages from the server to the client. There were no FDCs or errors written by the MQ code to indicate this condition exists.
Local fix
End and restart the application.
Problem summary
**************************************************************** USERS AFFECTED: Users of MQ's asynchronous consumer APIs from a client (eg. TCP/IP) program. Platforms affected: MultiPlatform **************************************************************** PROBLEM DESCRIPTION: This was a race condition where the two threads in the SVRCONN channel that serve the application changed a pointer in a data block that they both share. When this happened, a counter (the number of active consumers) being updated by one thread was updated on the wrong data block. So, later the counter was smaller than it should have been, and the decision logic running at that time, chose not to re-start the flow of messages to the client.
Problem conclusion
A resolution has been found to avoid the race condition, so that both of these threads can continue their work safely, avoiding the problem. --------------------------------------------------------------- The fix is targeted for delivery in the following PTFs: Version Maintenance Level v9.1 CD 9.1.5 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
IT31861
Reported component name
MQ APPLIANCE M2
Reported component ID
5737H4700
Reported release
914
Status
CLOSED PER
PE
NoPE
HIPER
YesHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2020-02-13
Closed date
2020-06-18
Last modified date
2020-11-18
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 APPLIANCE M2
Fixed component ID
5737H4700
Applicable component levels
[{"Line of Business":{"code":"LOB36","label":"IBM Automation"},"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SS5K6E","label":"IBM MQ Appliance"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"914"}]
Document Information
Modified date:
19 November 2020