VM66264: HUNG USERS/SYSTEM

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• In some virtual networking configurations/workloads, guests or
  the entire z/VM system can appear to hang.
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: Systems with frequent movement of VSWITCH    *
  *                 guests and external hosts could be affected. *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  ****************************************************************
  * RECOMMENDATION: APPLY PTF                                    *
  ****************************************************************
  VM users and servers may experience slower response over time
  due to an error in cleaning up IP Table entries in LANIPTBL.
  Tools that investigate storage use might find an unusually high
  number of IPNBK elements occupying free storage.
  

Problem conclusion

• Periodic maintenance for CP VSWITCH structures (HCPIPNPM) did
  not correctly check for a "wrap" condition for the LANIPTBL
  chain of IPNBK structures. If the IPNBK at the bottom was
  deleted at the beginning of the scan, the scan was terminated (a
  false "wrap" was registered). In a network with frequent
  movement this could result in only one IPNBK being deleted while
  several are added to the chain between maintenance cycles.
  
  This scenario made it clear that there is a potential negative
  impact to retaining IPNBK entries from outside hosts in the
  VSWITCH LANIPTBL. They must be processed (so the "old" entry of
  a guest can be removed when ownership of that IP address is
  moved to an external host) but they do NOT have to be retained.
  
  HCPIPNAR is updated to discard the new IPNBK if the source was
  an UPLINK port (i.e. the host claiming ownership is outside the
  VSWITCH).
  
  HCPIPNPM is updated to correctly test for wrapping the chain
  and to improve efficiency by releasing the IPNBK storage as
  the IPNBK is removed from the chain (instead of collecting a
  secondary IPNBK stack to be released later).
  

Temporary fix

• FOR RELEASE VM/ESA CP/ESA R640 :
  PREREQ: VM66196
  CO-REQ: NONE
  IF-REQ: NONE
  FOR RELEASE VM/ESA CP/ESA R710 :
  PREREQ: VM66196
  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:

  UM35461 UM35462

Modules/Macros

• HCPIPN
  

Fix information

• Fixed component name

  VM CP

• Fixed component ID

  568411202

Applicable component levels

• R640 PSY UM35461

     UP19/05/22 P 2001

• R710 PSY UM35462

     UP19/05/22 P 1902

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.