PH45424: CICS AS0002, SR0001, SM0002, PG0002 ABENDS DUE TO INVALID CHANNEL TOKEN

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• CICS may take multiple abends such as;
  
  DFHAS0002 applid A severe error (code X'0205') occurred in
  module DFHASXM.
  DFHSM0002 applid A severe error (code X'030D') has occurred in
  module DFHSMGF.
  DFHPG0002 applid A severe error (code X'1709') has occurred in
  module DFHPGCH.
  
  In the exception trace at offset x'1A' you will see that it
  completed with a Return code 02 (Exception) and Reason code 08 (
  Invalid Token ):
  
  AS 0205 ASXM *EXC* - BIND_CHANNEL_FAILED -
  FUNCTION(BIND_XM_CLIENT) CLIENT_REQUEST_BLOCK
  
  
  2-0000  00480000 0000022C 00000000 00000000
    0010  B4000000 00000000 04000208 00000000
    0020  00000000 00000000 00000000 1FE97070
    0030  00000000 00000000 00000000 00000000
    0040  00000000 00000000
  
  And when looking at the channel token at offset x'2C' you will
  find that address is not currently a getmained CHCB, it was
  freed prior by a different task.
  
  The problem is that when a parent task runs a child task, the
  child will get to its end and post the parent to wake up out of
  its FETCH ANY wait. At that point there is a race, if the parent
  runs first and frees the CHCB,  and then the CHCB is
  re-getmained for use for another copy channel from a new parent
  to a new child, the errors can result.
  
  Additional symptoms:
  KIXREVTT
  DFHAS0002
  DFHSR0001
  DFHSM0002
  DFHPG0002
  INVALID_TOKEN  CHANNEL_TOKEN  ICE_CHANNEL_TOKEN
  

Local fix

• NA
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: Various abends (AS0002, SM0002 and/or   *
  *                      PG0002 due to an invalid channel token. *
  ****************************************************************
  A parent transaction starts a child transaction with a
  RUN-TRANSID command, passing a copied channel to it. The
  parent then waits on an ECB in FETCH-CHILD (or FETCH-ANY)
  command processing. At some point, the child completes and
  drives DFHASRM commit to post the ECB to awaken the parent once
  more. Depending upon CICS transaction dispatching;  z/OS TCB
  dispatching and processor availability, either the child or
  the parent may run before the other at this point. If the parent
  runs first, it can rename the channel it receives back from the
  child and add it to its own set of channels. The parent may then
  end, freeing the channel and its CHCB control block - this means
  there is the potential for the CHCB to be GETMAIN'd again and
  reused for another channel passed between another parent and
  child transaction pair.
    When the original child transaction gets dispatched again, it
  finds that accb_channel_token is still set in the ACCB, so it
  deletes the channel and freemains the CHCB.
    This means the child has now freed the CHCB in use for another
  channel owned by another child transaction. This can lead to
  an AS0002, SM0002 and/or PG0002 abend, depending on what happens
  next in relation to the current usage of the channel and its
  (now freemained) CHCB. It can also prevent a new child from
  detaching its channel when it ends, if chcb_persistent does not
  happen to be on at that point in time due to the CHCB being
  freed and reused during that time.
  

Problem conclusion

• DFHASRM has been changed to test that the accb_channel_fetched
  flag is not set on before deleting the child's channel at the
  end of commit processing.
  

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:

  UI80973 UI80974 UI80975

Modules/Macros

• DFHASAS  DFHASRM
  

Fix information

• Fixed component name

  CICS TS Z/OS V5

• Fixed component ID

  5655Y0400

Applicable component levels

• R100 PSY UI80975

     UP22/06/11 P F206 ¢

• R200 PSY UI80974

     UP22/06/16 P F206 ¢

• R300 PSY UI80973

     UP22/06/15 P F206 ¢

Fix is available

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