A fix is available
APAR status
Closed as program error.
Error description
MQ threads hung due to latch contention where the latch was no longer held, but the waiter was not correctly resumed. Symptoms of the problem vary depending on which threads are waiting for the latch. For the reported case, messages built up on SYSTEM.CLUSTER.TRANSMIT.QUEUE because the channel was the latch waiter that was not properly resumed. The ROB control block for the waiting task had evidence that the resume had been attempted. The MVS RELEASE may have been done for a different Pause Element Token (PET) than was used for the pause. Unfortunately the point of detection is a long time after the problem occurred so it is difficult to fully investigate. This is similar to the situation in DB2 APAR PI55964 which provides additional diagnostic information to detect errors in the suspend and resume protocol. This APAR will port that code to MQ. Additional Symptom(s) Search Keyword(s): wait waiting hanging
Local fix
There is not a preventive work-around. The problem will be cleared by a queue manger recycle.
Problem summary
**************************************************************** * USERS AFFECTED: All users of IBM MQ for z/OS Version 9 * * Release 0 Modification 0 and Release 1 * * Modification 0. * **************************************************************** * PROBLEM DESCRIPTION: An MQ task that had been suspended by * * csqvsusp processing was not resumed * * as expected by csqvresm causing the * * task to hang. * * Dump analysis was not able to determine * * the cause of the hang. * * * * Additionally, in some situations * * diagnostic dumps requested by MQ are * * not successfully captured. * **************************************************************** A task issued CSQVSUSP to suspend processing until resumed by another task. CSQVRESM was issued for the associated ROB, however the suspended task remained paused. A dump taken when the hang was observed did not give sufficient information to determine why the resume request had not released the suspended task. Additional keywords: CSQWDSDM 0C4 S0C4
Problem conclusion
CSQVSRX is enhanced to check for unexpected changes in the state of a ROB, such as would be seen if a ROB was invalidly reused. If an invalid state is seen, a diagnostic dump is taken by CSQVSRX with abend code 5C6-00E5xxA1, where xx depends on the invalid state detected. In addition, an error in recovery processing that prevented some MQ dumps, included those added by this APAR, from being captured is fixed, allowing such diagnostic dumps to be produced.
Temporary fix
Comments
APAR Information
APAR number
PH12062
Reported component name
IBM MQ Z/OS V9
Reported component ID
5655MQ900
Reported release
000
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2019-05-14
Closed date
2019-06-28
Last modified date
2019-08-01
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UI63973 UI63974
Modules/Macros
CSQVSRRX CSQVSRX CSQWDSD0 CSQWDSDM
Fix information
Fixed component name
IBM MQ Z/OS V9
Fixed component ID
5655MQ900
Applicable component levels
Fix is available
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Document Information
Modified date:
01 August 2019