A fix is available
APAR status
Closed as program error.
Error description
You are running CICS Transaction server 5.4, using IPIC connections. When running a large volume workload, the region becomes unresponsive. A dump taken at the time of this hang showed the QR TCB was in a loop in module DFHDSKE. The stack for the running task shows it is in the process of terminating, when DFHDSKE attempts to free TCB's associated with the task. The modules from the stack are: NAME DFHKETA DFHDSKE RESUME_AWAIT . It is attempting to free the SSL pool TCBs or S8 TCBs, which are located at offset x'170' into the tasks DTA control block. The S8 TCB is represented by a DFHDSDS_TCB control block, and offset x'98' is field OWNED_FWD -Which is a pointer to tcbs of same open mode. In the dump, this field points to itself. There is a problem with the CISR transaction where it references an S8 TCB, that is being used by a different task, and incorrectly frees it putting it on the free chain, and leads to this loop. Additional Symptom(s) Search Keyword(s): KIXREVRJL
Local fix
Problem summary
**************************************************************** * USERS AFFECTED: All CICS users. * **************************************************************** * PROBLEM DESCRIPTION: CICS region becomes unresponsive due * * to a loop in DFHDSKE caused by an S8 * * TCB on the open TCB free chain pointing * * to itself. * **************************************************************** CICS is processing a heavy workload over an IPIC connection that is using SSL. A mirror task is sending back a large response to the partner system. At the same time a new request arrives on the same socket and CISR is resumed to handle it. The mirror task and CISR need to switch between the QR, SO and S8 TCBs to perform the socket I/O. Due to an error in the TCB management within the CICS sockets domain, it is possible for the CISR task to end up running on the same S8 TCB as the mirror task. When both tasks finish using the S8 TCB they issue a CHANGE_MODE with DISASSOCIATE_TCB(YES). Each of these cause the S8 TCB to be added to the open TCB free chain. The S8 TCB is now on the free chain twice and most likely points to itself. A loop will occur the next time the open TCB free chain gets processed and CICS will appear to be hung. Formatting the DS section of a dump that was taken at the time of the hang will cause IPCS to enter a loop.
Problem conclusion
The CICS web and sockets domain code used to process IPIC requests has been changed to correctly manage the TCB state when multiple tasks use the same socket.
Temporary fix
Comments
×**** PE18/11/20 FIX IN ERROR. SEE APAR PH05536 FOR DESCRIPTION
APAR Information
APAR number
PI99580
Reported component name
CICS TS Z/OS V5
Reported component ID
5655Y0400
Reported release
100
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2018-06-26
Closed date
2018-08-23
Last modified date
2019-03-21
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UI58045 PH10004
Modules/Macros
DFHISCO DFHISEM DFHISRR DFHISSR DFHMNXM DFHSOCK DFHWBCL DFHWBSO DFHWBSV DFHWBSVT DFHWBXM
Fix information
Fixed component name
CICS TS Z/OS V5
Fixed component ID
5655Y0400
Applicable component levels
R100 PSY UI58045
UP18/08/25 P F808
Fix is available
Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.
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Document Information
Modified date:
21 March 2019