VM66831: Z/VM 7.4 CP: FIX PACK - FEATURE 00 FIX 08

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• R740 Linear Service APAR
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: z/VM users with MDC on and more than 2G of   *
  *                 memory.                                      *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  ****************************************************************
  * RECOMMENDATION: APPLY PTF                                    *
  ****************************************************************
  This APAR for z/VM 7.4 Fix Pack 0008 contains fixes for the
  following problem(s):
  
  Problem 1: SYSTEM HANG DUE TO MDC CONSUMING LESS THAN 2G STORAGE
  
  The system hangs. MDC is on. It may be noticed that MDC has
  nearly all of memory in use below 2G. It is not known why this
  happens in rare cases. Examination of dumps showed over 95
  percent of memory less than 2G in use for MDC with available
  frames >2G. Since MDC data frames are not easily stolen, a
  request for a <2G frame ends up in frame table scan. In the
  extreme case, no frame can be found and the system hangs.
  

Problem conclusion

• Problem 1: SYSTEM HANG DUE TO MDC CONSUMING LESS THAN 2G STORAGE
  
  Logic is added to consumers of MDC frames to examine the ratio
  of MDC frames <2G to >2G and if skewed <2G then attempt to get a
  FRMTE conditionally from the >2G available zones. If this
  request fails, then the old path is used. This ensures a balance
  of MDC frames and no loop possible.
  

Temporary fix

• *********
  * HIPER *
  *********
  FOR RELEASE VM/ESA CP/ESA R740 :
  PREREQ: VM66821
  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:

  UM90506

Modules/Macros

• HCPCPE   HCPFMA   HCPFMP   HCPSTP   HCPSVGMR HCPTCM   HCPTCMBK
  7VMCPR40
  

Fix information

• Fixed component name

  VM CP CP

• Fixed component ID

  568411202

Applicable component levels

• R740 PSY UM90506

     UP25/03/14 P 2501 ¢

Fix is available

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