PH42541: DFHSO0126 FOLLOWED BY A DFHSO0002 (CODE 02A0 ) IN MODULE DFHSOCK

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The customer is reaching MAXSOCKETS limit - DFHSO0126. Then they
  start getting Severe error DFHSO0002 020A - CHANGE_MODE_ERROR
  trying to switch to an S8 TCB that is owned by a different task.
  Eventually this leads to a DFHDS0004 due to an S8 DS_TCB
  pointing to itself.
  ADDITIONAL KEYWORDS: KIXREVACC
  DFHSO0126 DFHSO0002 02A0 DFHSOCK MAXSOCKETS SSL
  A severe error (code X'080C') has occurred in module DFHSOSE
  A severe error (code X'02A0') has occurred in module DFHSOCK
  A possible loop has been detected at offset X'FFFF' in module
  DFHDSDS4.
  SO 02A0 SOCK  *EXC* -   FUNCTION(CREATE) TRANSPORT(TCP)
                 LIFETIME(SHARED) QUEUE_TIMEOUT(NO) SWITCH_TCB(NO)
  DS 0063 DSDS4 *EXC* - DSDS4_RECOVERY - FUNCTION(ASSOCIATE_OPEN)
                 CHANGE_MODE_PLIST(xxxxxxx) DS_TCB(yyyyyyyy)
  Loop occurs in routine ASSOCIATE_OPEN in DFHDSDS4 due to an
  DFHDSDS_TCB control block representing an S8 TCB pointing to
  itself. (next_open_free)
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: DFHSO0002 code(x'02A0') when CICS has   *
  *                      reached the MAXSOCKETS limit.           *
  ****************************************************************
  CICS is processing a large amount of outbound SSL requests.
  The volume of requests has caused CICS to reach the MAXSOCKETS
  limit.  When the next request is made, CICS attempts to find an
  idle socket to close.  DFHSOPL RECLAIM_SOCKET gets called to see
  if there are any suitable sockets sat in an outbound connection
  pool.
  
  On entry, DFHSOPL issues a CHANGE_MODE to the SO TCB.  This call
  specifies DISASSOCIATE_TCB(YES), which causes the current S8 TCB
  to be removed from the task and returned to the open TCB free
  chain.  On exit, DFHSOPL issues a CHANGE_MODE back to the
  original S8 TCB (using its token).  However, that TCB may now be
  owned by a different task.
  
  An S8 TCB should only ever be used by a single task at a time.
  The TCB being used by two tasks can cause any of the following
  symptoms;
  
  DFHSO0002 A severe error (code X'080C') has occurred in module
  DFHSOSE.
  DFHSO0002 A severe error (code X'02A0') has occurred in module
  DFHSOCK.
  DFHDS0004 A possible loop has been detected at offset X'FFFF' in
  module DFHDSDS4.
  

Problem conclusion

• DFHSOPL RECLAIM_SOCKET has been changed to retain ownership of
  the callers S8 TCB.
  

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:

  UI78887 UI78888 UI78889

Modules/Macros

• DFHSOM01 DFHSOPL
  

Fix information

• Fixed component name

  CICS TS Z/OS V5

• Fixed component ID

  5655Y0400

Applicable component levels

• R100 PSY UI78889

     UP22/01/13 P F201 ¢

• R200 PSY UI78888

     UP22/01/13 P F201 ¢

• R300 PSY UI78887

     UP22/01/13 P F201 ¢

Fix is available

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