PM94359: OBSOLETE VCRT ENTRIES CREATED DURING DVIPA MOVEMENT

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The Sysplex Distributor for a DVIPA maintains a VIPA Connection
  Route Table that identifies every active connection and the
  intended target system.  When the DVIPA ownership (SD function)
  is moved to another stack, the old distributor will send this
  table to the new distributor.
  
  If the new distributor was also a target for these connections
  before the movement, a timing window exists where connections on
  the new SD system can be closed during the movement process but
  the VCRT entry for that connection is transferred to the new
  distributor.  This VCRT entry will not go away since the SD
  function is expecting one more notification for ending the
  session than will ever be generated.
  
  If the SD function is later moved to another system (or back to
  the original), this obsolete entry will be transferred to the
  new SD.  After that point, any new connection attempts for that
  same 4tuple (source and destination IP address and port) will
  fail due to the associated target system discarding the SYN
  packets.
  

Local fix

• Forcing the affected target stack to leave the TCPIP sysplex
  will remove these obsolete entries.  This can be done with the
  following command:
  
     VARY TCPIP,,SYSPLEX,LEAVEGROUP
  
  Followed by a later VARY TCPIP,,SYSPLEX,JOINGROUP once that
  completes.  Otherwise, recycling the affected TCPIP stack is
  required.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of the IBM Communications Server   *
  *                 for z/OS Version 1 Release 13 IP:            *
  *                 Distributed DVIPA                            *
  ****************************************************************
  * PROBLEM DESCRIPTION: New connection attempts timeout         *
  *                      after Distributed DVIPA moved.          *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  A timing scenario exists during distributed DVIPA takeover
  which can cause entries to be added to the VCRT table
  that do not exist on the target stack. The problem can
  be summarized as follows:
  1. System A takes over ownership and distribution of a DVIPA
     that was previously a target DVIPA on System A.  System A
     has active connections using the DVIPA.
  2. The DVIPA changes ownership to System A.  The previous
     owner, System B, is notified.
  3. System B sends to System A all of the connections being
     distributed by System B for the DVIPA.
  4. Before System A can process the list of connections from
     System B, a distributed connection on System A ends and
     is removed from the VCRT on System A.
  5. System A then processes the list of connections from
     System B, adding back in the previously removed connection.
  6. A future connection reuses the ports but System A is no
     longer handling connections for that port, causing the
     connection to timeout.
  +-------------------------------------------------------------+
  + Please check our Communications Server for OS/390 homepages +
  + for common networking tips and fixes.  The URL for these    +
  + homepages can be found in Informational APAR II11334.       +
  +-------------------------------------------------------------+
  

Problem conclusion

• TCPIP has been modified to correctly process connections
  from the previous DVIPA owner which represent connections
  on the new DVIPA owner.
  
  * Cross Reference between External and Internal Names
  

Temporary fix

Comments

APAR Information

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

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

  UK97240 PM96751

Modules/Macros

• EZBXFACI EZBXFHSH EZBX6ACI EZBX6HSH
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R1D0 PSY UK97240

     UP13/10/05 P F310

Fix is available

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