PI96755: WMQ SYSTCPDD USED IN CHIN IS INTERMITTENTLY IGNORED, CAUSING NAME RESOLVER CALLS TO FAIL

Obtain the fix for this APAR.

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 8       *
  *                 Release 0 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 is sysrouted FROM one or more of the following:

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

  PH13517 UI64983

Modules/Macros

• CSQXPENT
  

Fix information

• Fixed component name

  IBM MQ Z/OS V8

• Fixed component ID

  5655W9700

Applicable component levels

• R000 PSY UI64983

     UP19/09/26 P F909

Fix is available

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