VM66235: SSI CLUSTER NOT STABLE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• In some cases, an SSI cluster becomes unstable, causing SSI
  functions to break.
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users running Single System Image        *
  *                 clusters                                     *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  ****************************************************************
  * RECOMMENDATION: APPLY PTF                                    *
  ****************************************************************
  SSI clusters sometimes cannot transition to Stable after a
  period of instability. This is especially prone to happen
  when ISFC connections are not stable.
  

Problem conclusion

• Three problems have been addressed:
  
  1. Cluster synchronization request responses are sometimes
     sent too late for the recipient to handle but nevertheless,
     the expected decision is still awaited. Eventually, a
     decision response does arrive, but it is for a subsequent
     request that hasn't been answered (because the previous
     one is still active), so the response is always "Abort".
     This sequence continues indefinitely and prevents the
     cluster from going stable.
  
     Reception of a late "Abort" is now remembered and causes
     the associated request to end immediately, allowing the
     system to catch up to the synchronization message traffic.
  
  2. Cluster synchronization request decisions are awaited
     indefinitely, so even if a link state change occurs
     because a link went down, the wait will persist until a
     decision (for a subsequent request) is received.
  
     Decision receive requests now time out, and if the link
     state indicates that a decision could not possibly be
     forthcoming, the request is aborted.
  
  3. A transition to STABLE mode might not be initiated if there
     is no associated change of the member to JOINED state.
  
     These transitions are initiated.
  

Temporary fix

Comments

• ×**** PE19/12/13 FIX IN ERROR. SEE APAR VM66101  FOR DESCRIPTION
  

APAR Information

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

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

  UM35410 UM35411

Modules/Macros

• HCPKCC   HCPKCD   HCPKCW   HCPMBHBK HCPPLM   HCPPMSBK
  

Fix information

• Fixed component name

  VM CP

• Fixed component ID

  568411202

Applicable component levels

• R640 PSY UM35410

     UP18/12/14 P 1901

• R710 PSY UM35411

     UP18/12/14 P 1901

Fix is available

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