PM30920: DFHWBXM LOOP NOT DETECTED WHEN DFHWBCL RETURNS EXCEPTION INVALID SESSION TOKEN.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Your CICS region appears to be hung within transaction
  CISC while acquiring an IPCON connection. The acquire
  connection fails and DFHWBXM is called for RELEASE_XM_CLIENT.
  .
  A corrupted WBO chain causes the QR KTCB to loop in DFHWBXM
  after calling DFHWBCL for function Close Session. DFHWBCL
  returns exception INVALID_SESSION_TOKEN and DFHWBXM fails
  to detect the exception, thus DFHWBXM continues to call DFHWBCL
  for ClOSE_SESSION.
  .
  Additional Symptoms and keywords: KIXFIXSWM
  .
  INVALID SESSION TOKEN  ACQUIRE_CONNECTION OPEN_SESSION
  TIMED_OUT SOCKET_ERROR ISCO XM_TXN_WB_TOKEN
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All                                          *
  ****************************************************************
  * PROBLEM DESCRIPTION: Loop in DFHWBXM during task termination *
  *                      after a corruption of the chain of WBO  *
  *                      blocks owned by the terminating task.   *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  A CISC task opens a number of outbound HTTP connections and
  creates two WBO blocks for each IPCONN which the CISC task is
  acquiring. The WBO blocks are added to a chain owned by the
  CISC task as each outbound connection is activated.
  The CISC task loses control attempting to ACQUIRE one of the
  IPCONNs.
  While CISC is suspended, a CIST task is attached to release
  one of the IPCONNs which the CISC task has previously ACQUIRED.
  CIST closes the outbound HTTP connections for the selected
  IPCONN and freemains the WBO blocks for them.
  The CIST task now completes.
  Eventually the CISC task times out and starts to terminate.
  During task termination, DFHWBXM RELEASE_XM_CLIENT is called to
  perform cleanup of its task local WBO chain. Normally WBO blocks
  for IPIC connections are retained by DFHWBXM.
  However, the WBO chain is no longer valid as WBO blocks have
  been freed.
  DFHWBXM loops through the WBO chain and calls DFHWBCL function
  CLOSE_SESSION for the first WBO. This WBO has already been
  freemained.
  Normally DFHWBCL will remove the WBO from the WBO chain and
  promote the next WBO to be the head of the WBO chain.
  However, DFHWBCL detects that the WBO SESSION_TOKEN passed is
  invalid so an EXCEPTION is returned to DFHWBXM with reason
  WBCL_INVALID_SESSION_TOKEN. DFHWBXM fails to detect the error.
  It iterates the WBO loop and selects the same WBO from the head
  of the WBO chain and repeats the call to DFHWBCL.
  DFHWBXM RELEASE_XM_CLIENT runs in a phase of task termination
  where runaway detection is disabled. CICS therefore loops until
  it is cancelled.
  

Problem conclusion

• DFHWBCL OPEN_SESSION has been changed to bypass the code which
  adds a WBO to the task local WBO chain when the WBO is for an
  IPIC session.
  DFHWBXM RELEASE_XM_CLIENT is changed to detect when an error is
  returned from DFHWBCL CLOSE_SESSION which leaves the selected
  WBO at the head of the WBO chain. When this occurs the chain is
  assumed to be corrupted and the loop is terminated. A DFHWB0002
  message with system dumpcode WB0002 will be produced in these
  circumstances. Exception trace WB 060D will also be produced.
  The CICS TS for z/OS Version 4 Release 1 Trace Entries manual
  ( SC34701301 ) will be updated. In Chapter 49 ( Web domain
  trace points ) the following new entry will be inserted :-
  
  Point ID    Module   Lvl    Type         Data
  WB 060D     DFHWBXM  Exc    Close error  1 XMAC parameter list
                                           2 WBCL parameter list
  

Temporary fix

•             *********
              * HIPER *
              *********
  FIX AVAILABLE BY PTF ONLY
  

Comments

APAR Information

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

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

  UK65372

Modules/Macros

•    DESWBAN  DESWBAP  DESWBCL  DESWBDM  DESWBRQ
  DESWBRQF DESWBSR  DESWBXM  DFHWBANC DFHWBAND DFHWBAP  DFHWBAPA
  DFHWBAPF DFHWBAPJ DFHWBAPM DFHWBAPT DFHWBAPV DFHWBCL  DFHWBDCC
  DFHWBDCD DFHWBDM  DFHWBRQD DFHWBRQS DFHWBSR  DFHWBSRA DFHWBSRM
  DFHWBSRT DFHWBTRI DFHWBXM  DFHWBXMA DFHWBXMT
  

Fix information

• Fixed component name

  CICS TS Z/OS V4

• Fixed component ID

  5655S9700

Applicable component levels

• R600 PSY UK65372

     UP11/03/08 P F103

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.