VM66209: SYSTEM HANG CAN OCCUR WITH MD CACHING ON

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• In some cases, a CPU can be stuck in a loop when Minidisk
  Caching is on.
  
  Eventually this will cause a system hang or abend.
  

Local fix

• This problem can be circumvented by issuing the CP SET MDC
  SYSTEM OFF command.  While this command avoids the problem, it
  might cause performance degradation.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of Minidisk Cache.                 *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  ****************************************************************
  * RECOMMENDATION: APPLY PTF                                    *
  ****************************************************************
  In some cases, a CPU can be stuck in a loop while Minidisk
  Caching is on. This will cause a system hang.
  

Problem conclusion

• A LA instruction in HCPFMI, in 31 bit addressing mode, resulted
  in the address 7FFFFFF8 being incremented to 0 rather than
  80000000. This resulted in the subsequent CR/BrNH branching when
  it should have fallen through.
  Code in HCPFMI was changed such that a AHI instruction was used
  for the addition and a CLR was used for the test.
  

Temporary fix

• FOR RELEASE VM/ESA CP/ESA R640 :
  PREREQ: NONE
  CO-REQ: NONE
  IF-REQ: NONE
  FOR RELEASE VM/ESA CP/ESA R710 :
  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:

  UM35370 UM35371

Modules/Macros

• HCPFMI
  

Fix information

• Fixed component name

  VM CP

• Fixed component ID

  568411202

Applicable component levels

• R640 PSY UM35370

     UP18/10/05 P 1901

• R710 PSY UM35371

     UP18/10/05 P 1901

Fix is available

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