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PH13517: MQ SYSTCPDD USED IN CHIN IS INTERMITTENTLY IGNORED, CAUSING NAME RESOLVER CALLS TO FAIL

A fix is available

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APAR status

  • Closed as program error.

Error description

  • Intermittently the MQ CHIN will experience name resolver errors
    due to the SYSTCPD DD not being loaded based on its PROC.
    GetHostByName calls can fail with errors such as
    GetHostByName Failed:  RetVal = -1, RC = 1, Reason = 0x78981005
    GetHostByName Ended: year/mm/dd hh:mm:ss.subsec
    -
    The local TCP/IP dataset unexpectedly is /etc/resolv.conf
    instead of the reference set using SYSTCPD DD. As well, the
    caller API is LE C Sockets instead of USS (Unix System Services)
    -
    In the instances where resolution is successful, the caller API
    is USS. Resolution will complete successfully if the MQ
    subsystem is recycled.
    Hursley Change Team and CommServer find that, as there are two
    types of API mode (LE and USS) the first type of call to be used
    sets the affinity for any subsequent calls within the address
    space.
    -
    If the first type of call is not through USS then the PrliCICS
    flag that re-enables the check for //DD:SYSTCPD is ignored.
    -
    Code change may include a dummy USS-based DNS lookup during
    CHINIT initialization to ensure that MQ explicitly establishes
    affinity to the USS API
    

Local fix

  • Recycle MQ CHIN
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
    *                 Release 0 Modification 0 and Release 1       *
    *                 Modification 0.                              *
    ****************************************************************
    * PROBLEM DESCRIPTION: Occasionally the SYSTCPD or SYSTCPDD    *
    *                      card is being ignored on chinit startup *
    *                      resulting in failed DNS resolver        *
    *                      calls.                                  *
    ****************************************************************
    A race condition between different tasks on the same process
    during chinit startup occasionally results in the process not
    being treated as a USS caller.
    
    In this case the DD cards SYSTCPD or SYSTCPDD are being ignored
    and can result in failed DNS resolver calls.
    

Problem conclusion

  • The race condition has been removed thereby ensuring that the
    process in question is always correctly identified as a USS
    caller.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PH13517

  • Reported component name

    IBM MQ Z/OS V9

  • Reported component ID

    5655MQ900

  • Reported release

    000

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2019-06-18

  • Closed date

    2019-08-27

  • Last modified date

    2019-10-01

  • APAR is sysrouted FROM one or more of the following:

    PI96755

  • APAR is sysrouted TO one or more of the following:

    UI64985 UI64986

Modules/Macros

  • CSQXPENT
    

Fix information

  • Fixed component name

    IBM MQ Z/OS V9

  • Fixed component ID

    5655MQ900

Applicable component levels

  • R000 PSY UI64986

       UP19/09/26 P F909

  • R100 PSY UI64985

       UP19/09/25 P F909

Fix is available

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Document Information

Modified date:
01 October 2019