A fix is available
APAR status
Closed as program error.
Error description
An allied thread (in the customer's case, CICS) was cancelled in a must complete state due to an unexpected abend 878. To prevent an integrity issue, the queue manager must terminate, and would require to be started once termination is complete. However, due to a timing window as a result of the manner the allied threads were cancelled, MQ was unable to gracefully come down, resulting in delays in the termination. During the termination process further abends occurred when applications were attempting new connections to the queue manager. Due to the small timing window hit in this rare circumstance, recovery processing entered a spin loop. The spin loop may eventually result in SCOM being overlaid with 10 bytes. If such overlay happens, abends 5C6-00E80031 can occur in applications connecting to MQ due to validation failing early in the connect. They happen prior to the MQ termination completion.
Local fix
Avoid unexpected allied address spaces termination, such as circumstances that lead to abends 878, 80A, 40D.
Problem summary
**************************************************************** * USERS AFFECTED: All users of IBM MQ for z/OS Version 9 * * Release 1 Modification 0. * **************************************************************** * PROBLEM DESCRIPTION: Various symptoms occur if CSQVSRX is * * called while the CPU lock is held. * * Symptoms include: * * - Abend 5C6-00E80031 in CSQYALLI * * - overlay of the MQ SCOM control block * * with 10 bytes ending 'CSQVSTRM' * * - disabled loop in recovery processing * * - repeated 073 abends reported in * * logrec * **************************************************************** An MQ task was dispatched on a TCB with the CPU lock unexpectedly held, and the task then called CSQVSRX to suspend or resume a ROB. CSQVSRX detected that the lock was unexpectedly held, and abended 5C6-00E50050, causing CSQVSRRX to be called as part of recovery processing. CSQVSRRX determined that the queue manager should be terminated by CSQVATRM, however this abended S073 due to the CPU lock being held. An error in MQ recovery processing caused the 073 abend to be retried incorrectly, leading to the SCOM being overlaid, and another call to CSQVATRM. MQ recovery processing continued to loop until the disabled loop was detected by the system and the queue manager was terminated.
Problem conclusion
MQ abnormal termination processing (CSQVATRM) is changed to better tolerate being called with the CPU lock held, so that the intended abnormal termination of the queue manager can complete.
Temporary fix
Comments
APAR Information
APAR number
PH20899
Reported component name
IBM MQ Z/OS V9
Reported component ID
5655MQ900
Reported release
100
Status
CLOSED PER
PE
NoPE
HIPER
YesHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2020-01-10
Closed date
2020-02-19
Last modified date
2020-04-02
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UI67983
Modules/Macros
CSQ3EXT2 CSQVATRM CSQVATRR CSQWDSDM
Fix information
Fixed component name
IBM MQ Z/OS V9
Fixed component ID
5655MQ900
Applicable component levels
R100 PSY UI67983
UP20/03/11 P F003 ¢
Fix is available
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Document Information
Modified date:
27 March 2020