A fix is available
APAR status
Closed as program error.
Error description
ABN=5C6-00A30042,U=SYSOPR ,C=R3600.710.SMC -CSQSHGMN,M=CSQ GFRCV,LOC=CSQSLD1 .CSQSHGMN+00000F20 . Reason 00A30042 means a 64-bit allocation failed. . The SMC=2 or SMC=3 keyword for the CSQWDPRD dump formatter showed a high number of 64bit heaps for the Storage Allocation Block ( SAB ) for "Heap for TOPM tree & msg props". . RSMDATA HIGHVIRT ASID(x'yy') DETAIL demonstrated a pattern of above-the-bar storage being obtained at intervals matching the EXPRYINT setting. . The failing thread was EXPWRK01 for expiry / expiration. Its Register Save Area indicated a sequence of CSQIEXP2, CSQIMGET, CSQIMGES, CSQMHDRS, CSQTZR0W, and CSQSHGMN. . Expiry processing was occurring for a shared queue containing messages with chained headers that require parsing. . For the problem to manifest itself, UI13788 needs to be on CSQIEXP2, and the expiry task needs to process a very specific sequence of messages on a single queue (starting with a message containing chained headers). Control information related to those chained headers needs to match a very specific bit pattern in order for the right flags to be set on the subsequent call that parses message properties. . 4KB of storage is leaked per message processed when the special pattern is met. Low queue depths will limit the exposure to the problem. . Follow-on symptoms may include: - ABN=5C6-0EA75417,U=XHM1CHIN,C=R3600.710. -UNKNOWN,M=CSQGFRCV, LOC=CSQMCGLM.CSQMCPRH+00002B64 - ABN=5C6-00E7014F,C=R3600.710.CHIN,LOC=CSQXADPM.CSQXADPM+05268 Additional Symptom(s) Search Keyword(s): ABEND5C6 ABENDS5C6 5C6 S5C6 S05C6 00A30042 0EA75417
Local fix
If possible, set EXPRYINT to OFF in the QMGR: /cpf ALTER QMGR EXPRYINT(OFF) where "cpf" is the command prefix for the queue manager. . Another option is to back out UI13788.
Problem summary
**************************************************************** * USERS AFFECTED: All users of WebSphere MQ for z/OS Version 7 * * Release 1 Modification 0. * **************************************************************** * PROBLEM DESCRIPTION: After applying UI13788, the queue * * manager runs out of above the bar * * storage. The queue manager may abend * * with 5C6-00A30042. * **************************************************************** * RECOMMENDATION: * **************************************************************** When an expiry task processes a shared queue, it does a browse of the message. This processing requires a valid handle. The processing is done in a lightweight fashion, and only a partial handle is obtained. If CSQIEXP2 is processing a message containing an RFH2 header, the MMC_SEG_CHAINED_HEADERS segment in the parameters will be populated. When CSQMHDRS checks the MHND MsgPropFlags to check if message properties need to be extracted, it looks beyond the storage obtained for the partial MHND block and effectively looks at CSQIEXP2 stack storage. In particular the pointer to the RFH2 header in the MMC_SEG_CHAINED_HEADERS segment. Depending on the address, fWantMsgHandle may appear to be set in the incorrectly referenced storage. zrfParse will obtain storage for message properties (ZRFP blocks). CSQMHDRS will not release that storage if the RFH2 header has been parsed. This happens if the message was put to a shared queue: - hosted on CFLEVEL(5) OFFLOAD(SMDS) structures when the shared queue has the PROPCTL(V6COMPAT) attribute set - hosted on CFLEVEL(5) OFFLOAD(DB2) or CFLEVEL(x), where x < 5, structures The storage is not released in CSQMHDRS because it is the getting applictions responsibility to do so. As CSQIEXP2 does nothing with the properties, the storage is leaked.
Problem conclusion
The code in CSQIEXP2 was changed to obtain a full MHND block at prevent CSQMHDRS from looking at storage that is used for a different purpose. 100Y CSQESYNC CSQIEXP1 CSQIEXP2 CSQIMGES CSQMOLNO CSQMREF2
Temporary fix
********* * HIPER * *********
Comments
APAR Information
APAR number
PI28977
Reported component name
WMQ Z/OS V7
Reported component ID
5655R3600
Reported release
100
Status
CLOSED PER
PE
YesPE
HIPER
YesHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2014-11-04
Closed date
2014-11-26
Last modified date
2015-02-03
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
PI29037 UI23450
Modules/Macros
CSQESYNC CSQIEXP1 CSQIEXP2 CSQIMGES CSQMOLNO CSQMREF2
Fix information
Fixed component name
WMQ Z/OS V7
Fixed component ID
5655R3600
Applicable component levels
R100 PSY UI23450
UP15/01/16 P F501 «
Fix is available
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Document Information
Modified date:
03 February 2015