A fix is available
APAR status
Closed as program error.
Error description
Monitoring data shows a high number of CSSY tasks. Besides there being a high number of tasks, their average response time is almost half a second. For example, one customer encountered about one CSSY task per minute per CICS region. They had an average response time of 0.4 seconds per task. This put the CSSY tasks consistently as the longest running tasks in their system. . Transaction CSSY is an internal CICS task. It can be started for many different reasons. In this case, most of the tasks were attached by DFHAPATT to check for a clock mismatch because of SIT option AUTORESETTIME=IMMEDIATE. With this option set, each time a task is dispatched or DFHZDSP runs in a TOR (after APAR PI39631) CICS checks to see if its clock is different than the system clock. If it is, it attaches a CSSY task to do more checking to see if CICS needs to automatically adjust its clock. The code only compares hours, minutes and seconds but no subseconds (HHMMSS). The CSSY may be attached when the check happens at about the same time as the clock is changing from one second to the next. In that case the CICS clock and system clock may be on either side of the second boundry, for example CICS clock = 10:11:11.9999 System clock = 10:11:12.0001 In this case, because the subsecond values are not used, the compare thinks the timestamps may be different. A CSSY task is attached to look at it further. The first thing the CSSY task does is delay itself for 0.2 seconds. This allows both clocks to get closer to the middle of a second time. Then, the compare would match and the CSSY task would simply end without taking any action. . This APAR is being taken to investigate whether the code could be changed - to use math to look at the difference between the clocks - instead of a simple compare. The math could detect that there is less than one second difference between the clocks and avoid attaching the CSSY tasks at all. That would save the time taken to attach, run and terminate all of the CSSY tasks. It would also remove the large number of CSSY tasks from the monitor reports so that they don't impact customer research time to see what the tasks are for. KIXREVDWZ
Local fix
Ignore the monitor report. The response time delay is part of normal processing for CSSY tasks started for clock checking.
Problem summary
**************************************************************** * USERS AFFECTED: * * All. * **************************************************************** * PROBLEM DESCRIPTION: * * Excessive attaches of system task CSSY. * **************************************************************** * RECOMMENDATION: * * . * **************************************************************** This problem presents when the AUTORESETTIME=IMMEDIATE SIT parameter is in use. . When AUTORESETTIME=IMMEDIATE is coded, DFHAPIN will test the MVS and CSA clocks to a granularity of seconds. If they are out by 1s or more then it attaches a CSSY system task to investigate the mismatch further and possibly do a DFHIC reset if the mismatch is a genuine one. As would be the case when the MVS time is adjusted forwards or backwards, or when a leap second adjustment is made within MVS. . However, if the MVS and CSA times are at different seconds but the difference is less than a second, for example: MVS Time = 11:33:15.00 CSA Time = 11:33:14.99 Difference = 0.01 seconds. then currently DFHAPIN would still attach a CSSY task - even though the real difference is only 0.01 of a second. This is unnecessary and could be avoided by DFHAPIN filtering out these perceived mismatches prior to attaching a new CSSY system task. Keywords: CVTLSO CVTLSOH CVTLSOL
Problem conclusion
DFHAPIN has been modified and will now attach a CSSY task if the CICS and MVS times differ because of leap second adjustment, or for all cases unless the MVS time appears only one second ahead. . The following change will be made to the CICS Transaction Server for z/OS Version 5 Release 3 Data Areas Manual GC34-7406-00. . The CSA ( DFHCSAPS ) will be updated as follows: . A new bit CSALSADD will be added within byte CSAICIND thus: . Offset Type Len Name(Dim) Description (5B) 11.. .... * Reserved (5B) ..1. .... CSALSADD Leap Second Adjustment . In addition, a previously unused 2 byte field ( following CSACPSMW ) will now be named field CSALSO thus: . Offset Type Len Name(Dim) Description 72 Character 2 CSALSO Leap seconds offset
Temporary fix
Comments
APAR Information
APAR number
PI58560
Reported component name
CICS TS Z/OS V5
Reported component ID
5655Y0400
Reported release
000
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2016-03-04
Closed date
2016-07-28
Last modified date
2016-09-02
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UI39719
Modules/Macros
DFHAPIN DFHCSAD DFHSIA1
GC34740600 |
Fix information
Fixed component name
CICS TS Z/OS V5
Fixed component ID
5655Y0400
Applicable component levels
R000 PSY UI39719
UP16/08/05 P F608
Fix is available
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Document Information
Modified date:
02 September 2016