VM66184: HTT001 IN HCPDSB DURING SNAPDUMP PROCESSING

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• An HTT001 abend may occur in HCPDSB near label READYMST while
  a SNAPDUMP is in effect.
  This problem surfaces when SNAPDUMP marks the master
  processor for quiesce.
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: Any customers of z/VM using the SNAPDUMP     *
  *                 function.                                    *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  ****************************************************************
  * RECOMMENDATION: APPLY PTF                                    *
  ****************************************************************
  When the SNAPDUMP function is in effect, the system could
  abend with an HTT001. This may occur when SNAPDUMP processing
  changes the master's PFXTYPE to PFXTYOFL to signal him to
  quiesce, but before the dispatcher can respond to the quiesce.
  Any code that tests PFXTYPE=PFXMASTR which runs during this
  window of time will take the wrong branch. HCPDSB is the only
  such place where a hard abend will occur as a result.
  
  The Greater than 64 Infrastructure support included in the
  base of z/VM 7.1 makes the HTT001 possible, however the
  window of time where the error can occur is small. This
  means that the occurrence of this abend is unpredictable and
  can not be circumvented without this APAR.
  

Problem conclusion

• The bad test and branch was replaced with a test that is not
  sensitive to SNAPDUMP's quiesce function. The code remains
  logically the same, but eliminates the bug that causes
  a bad branch decision. With the fix it is impossible to execute
  the code that signals the Master while running on the Master
  even when the executing processor is in the pending quiesce
  state.
  

Temporary fix

• FOR RELEASE VM/ESACP/ESAR710 :
  PREREQ: NONE
  CO-REQ: NONE
  IF-REQ: NONE
  

Comments

APAR Information

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

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

  UM35340

Modules/Macros

• HCPDSB   HCPSTK
  

Fix information

• Fixed component name

  VM CP

• Fixed component ID

  568411202

Applicable component levels

• R710 PSY UM35340

     UP18/07/19 P 1801

Fix is available

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