PH64812: CICS GETS DFHSO0002 (CODE X'02A0') CONDITIONS AFTER REACHING MAXSOCKETS LIMIT

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• A slow down of outbound SSL workload was leading to a MAXSOCKETS
  limit reached condition (message DFHSO0126) in a CICS region.
  Subsequently, the following errors are logged:
  
  DFHSO0002 A severe error (code X'02A0') has occurred in module
  DFHSOCK.
  
  The trace showed a CHANGE_MODE error which was issued when an
  attempt is made to switch back onto the callers S8 TCB. This
  fails because the TCB is no longer available (because the
  association was lost as part of processing the closure of the
  reclaimed socket).
  
  Trace entry:
  *EXC* CHANGE_MODE_ERROR FUNCTION(CREATE) TRANSPORT(TCP)
  QUEUE_TIMEOUT(NO) TIMEOUT_VALUE(1) PROTOCOL(HTTP) SWITCH_TCB(NO)
  
  
  
  This is a variation of the issue addressed by APAR PH42541
  which presents itself when MAXSOCKETS is reached and there is an
  eligible socket in the pool to be closed and reclaimed for the
  current request.
  

Local fix

• Make sure that the MAXSOCKETS limit isn't reached.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS Users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: Message DFHSO0002 can be seen as the    *
  *                      result of a CHANGE_MODE error when a    *
  *                      region is at MAXSOCKETS.                *
  ****************************************************************
  When a CICS region is at MAXSOCKETS and an attempt is made to
  reclaim a socket to be used for a secure inbound HTTP request,
  a change_mode error can be seen when the socket to be reclaimed
  has been used for secure/SSL work. This is because the task
  has lost association to its S8 TCB as CICS incorrectly assumes
  the S8 TCB is being used temporarily in order to close the
  secure socket being reclaimed.
  

Problem conclusion

• CICS now caters for the situation where a task already owns an
  S8 TCB, and the switch to an S8 in order to close a secure
  socket for re-use is not temporary.
  

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:

  UO05733 UO05734 UO05735 PH68909

Modules/Macros

• DFHSOAD  DFHSOCK  DFHSODM  DFHSODUF DFHSOIS  DFHSOL   DFHSOLI
  DFHSOLS  DFHSOLX  DFHSOLX6 DFHSOM01 DFHSOM02 DFHSOM03 DFHSOPL
  DFHSOPLT DFHSORD  DFHSOS00 DFHSOS01 DFHSOS02 DFHSOS03 DFHSOS04
  DFHSOS05 DFHSOS06 DFHSOS07 DFHSOS08 DFHSOS09 DFHSOS10 DFHSOS11
  DFHSOS12 DFHSOS13 DFHSOS14 DFHSOS15 DFHSOS16 DFHSOS17 DFHSOS18
  DFHSOS19 DFHSOS20 DFHSOS21 DFHSOS22 DFHSOS23 DFHSOSE  DFHSOST
  DFHSOTB  DFHSOTI  DFHSOTRI DFHSOUE  DFHSOXM  DFHWBCL  DFHWBSC
  DFHWBUR
  

Fix information

• Fixed component name

  CICS TS Z/OS V6

• Fixed component ID

  5655YA100

Applicable component levels

• R400 PSY UO05735

     UP25/11/12 P F511

• R500 PSY UO05734

     UP25/11/12 P F511

• R600 PSY UO05733

     UP25/11/12 P F511

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.