PH61179: DFHDS0001 0C1/AKEA IN DFHDSTCB WITH 2 CONSOLE TASKS SHARING THE SAME TCTTE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• CICS abends after taking an 0C1 due to a wild branch:
  
  DFHDS0001 An abend (code 0C1/AKEA) has occurred at offset
  X'FFFF' in module DFHDSTCB.
  
  Two CEMT tasks are entered at almost the same time on the MVS
  console. The first CEMT request causes a CATA task to be created
  to autoinstall the console TCTTE.  The 2nd console input finds
  that a console TCTTE is being autoinstalled so it remains on a
  queue to be checked later every time the TCP task runs.
  
  The problem happens when the CATA task does a GETMAIN for
  AI-TIOA storage and suspends on the SMLOCK. This causes the CATA
  task to lose control of the QR TCB.  This allows the TCP task to
  come back to life and try again to process the 2nd console
  input.  The TCP task finds that the console TCTTE has now been
  autoinstalled by the first request and now it tries to GETMAIN
  TIOA storage but suspends on the SMLOCK.
  
  The CATA task wakes back up after getting the SMLOCK, and
  attaches the first CEMT task.  But when the TCP task wakes up
  after getting the SMLOCK, it proceeds to attach a CEMT too and
  is successful. But both CEMT tasks are now associated with the
  same console TCTTE.
  
  There is code in DFHZATT that looks like it would prevent this
  problem but it is only executed for VTAM terminals.
  
  Additional Symptom(s) Search Keyword(s):
  DFHZATA2  DFHZCNA  TCTE_TRANNUM  abend0C1 abendS0C1 S0C1
  unpredictable results
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: CICS receives several CEMT commands     *
  *                      issued in quick succession from a       *
  *                      console. Two of the commands get given  *
  *                      the same console name and are running   *
  *                      at the same time. An 0C1 occurs.        *
  ****************************************************************
  There is a window in DFHZATA2 console attach where console
  autoinstall can create a TCTTE but suspend and lose control
  of the QR TCB.
  This allows TCP to run again and check the console deferred
  queue. If TCP finds another command issued from the same
  console it will use the TCTTE it created for the suspended
  command.
  CSTP will continue attaching both transactions, but they will
  both be running on the same console/terminal which should not be
  possible. This resulted in a corruption causing an 0C1 abend.
  

Problem conclusion

• DFHZCNA and DFHZATA2 have been changed to check if there is
  an attach pending on the TCTTE, and to defer the processing of
  the command if there is.
  
  The CICS Documentation will be updated for TCTTE - TCT terminal
  entry in the DATA AREAS section Table 1.
  
  (A4)  BIT(8)    1     TCTTEDII        DYNAMIC INSTALL indicators
  (A4)  1... ....       TCTTEDAP        Pending DYNAMIC ADD
  (A4)  .1.. ....       TCTTEDDP        Requires deleting
  (A4)  ..1.. ....      TCTEATTP        ATTACH in progress
  (A4)  ...1 ....       *               Reserved
  

Temporary fix

Comments

APAR Information

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

  PH60088

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

  UI97445

Modules/Macros

• DFHTCTTE DFHTCTZE DFHZATA2 DFHZCNA
  

Fix information

• Fixed component name

  CICS TS Z/OS V6

• Fixed component ID

  5655YA100

Applicable component levels

• R400 PSY UI97445

     UP24/06/27 P F406

Fix is available

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