A fix is available
APAR status
Closed as program error.
Error description
Running CICS TS 5.3 you receive the following message and then the region crashes. DFHDS0001 applid An abend (code 0C4/AKEA) has occurred at offset X'0DF8' in module DFHDSTCB. A dump at the time of the program check showed the failing instruction was: 9201 5041 | MVI X'41'(R5),X'01' R5 contained a bad value, causing the ABEND0C4. R5 was loaded from R2 which also contained the bad value. Backing up in the code found R2 was loaded from R8+130. R8 should be point to the task's DFHXMTxn - the transaction manager transaction control block, but the area did not have the correct eye catcher: >dfhxmtxn at the beginning of it. Trace was active in this dump, and we were able to learn the transaction was actually in the process of terminating. Transaction manager- XM was cleaning up the task when it was suspended requesting the SMLOCK. .. This was after a time where it had already freemained the DFHXMTxn control block for the task. This allowed storage manager to free up the entire page of storage it belonged on, allowing another task to allocate the storage. When the terminating task was attempted to be resumed, DFHDSTCB referenced this DFHXMTxn address from the task's DTA control block, which still had a pointer to it, leading to program check since it no longer reflected a DFHXMTxn. Here are the modules in the kernel stack for the task in the process of terminating: NAME DFHKETA DFHDSKE DFHXMTA DFHXMLD DFHXMQD DELETE_INSTANCE DFHAPDN APDN_TRANDEF_NOTIFY FREE_TRANDEF_STG DFHSMGF SMLOCK_GET DFHLMLM LOCK LOCK_EXCLUSIVE ADD_TO_LOCK_QUEUE SUSPEND DFHDSSR POP_TASK Additional Symptoms: KIXREVRJL
Local fix
Problem summary
**************************************************************** * USERS AFFECTED: All CICS users * **************************************************************** * PROBLEM DESCRIPTION: DFHDS0001 abend 0C4 /AKEA in * * DFHDSTCB. * **************************************************************** A transaction completed, and DFHXMTA was called to free the XMT storage for it. However, DFHXMTA did not clear the address of the XMT from the DTA, held in field DTA_XM_TKN. Having freemained the XMT, the transaction then continued and suspended on the SMLOCK within routine unlock_trandef_inline. This allowed another transaction to run. The storage that had been used for the XMT was reused for another subpool. When the first transaction was redispatched, DFHDSTCB ran and tried to update the WLM performance block, addressed from the XMT via the DTA. Since DTA_XM_TXN was not null, DFHDSTCB used this pointer to address what it believed was still a valid XMT. Since the DS_PB_TOKEN was not valid within the reused storage, this led to an 0C4/AKEA abend and CICS terminated. KEYWORDS: DSTCB PUSH_TASK
Problem conclusion
DFHXMTA has been changed to clear DTA_XM_TXN when the XMTXN is freemained within free_transaction.
Temporary fix
Comments
APAR Information
APAR number
PH26488
Reported component name
CICS TS Z/OS V5
Reported component ID
5655Y0400
Reported release
000
Status
CLOSED PER
PE
NoPE
HIPER
YesHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2020-06-16
Closed date
2020-07-24
Last modified date
2020-08-03
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UI70741 UI70742 UI70743 UI70744
Modules/Macros
DFHXMTA
Fix information
Fixed component name
CICS TS Z/OS V5
Fixed component ID
5655Y0400
Applicable component levels
R000 PSY UI70741
UP20/07/28 P F007 ¢
R100 PSY UI70742
UP20/07/25 P F007 ¢
R200 PSY UI70744
UP20/07/25 P F007 ¢
R300 PSY UI70743
UP20/07/25 P F007 ¢
Fix is available
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Document Information
Modified date:
05 August 2020