OA37305: LOOP IN ISTTSCWU WITH SHAREACB ENABLED

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Loop occurs in VTAM module ISTTSCWU while Telnet server is
  configured with SHAREACB parameter statement.
  Other symptoms:
  You may also see an ABEND0A9 FF13 in VTAM module
  ISTCPCDR and IXC431I and IXC633I messages.
  An ABEND0C4 in ISTTSCWU may occur.
  In the VIT, CPRC in module ISTCPCDR may be
  seen with a sense code of x'08400007'.
  

Local fix

• Code (or default) NOSHAREACB.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users who specify SHAREACB in            *
  *                 their Telnet profiles.                       *
  ****************************************************************
  * PROBLEM DESCRIPTION: Loop in ISTTSCWU due to a corrupted     *
  *                      TSEXT_TN_RDTES chain.                   *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The problem may be summarized as follows:
  1. The Telnet profile has SHAREACB coded.
  2. Some action occurs to bring down the VTAM
     session and cleanup VTAM's RDTE for a Telnet
     LU name (such as a client disconnect or the
     stopping of the Telnet server).
  3. The RDTE cannot be freed because VTAM is
     waiting for the FMCB to be freed and so the
     RDTE is queued on TSEXT_TN_RDTES chain.
  4. The FMCB is freed during UNBIND response
     processing.
  5. The PLU tries to redrive the session to the
     Telnet LU name.
  6. The RDTE is found, but its state causes the
     session to fail with an 0801000C sense code.
  7. The cleanup of the new session is allowed to
     free the RDTE because the FMCB has been freed.
  8. Later, when the Wake Up Pab processes the
     TSEXT_TN_RDTES chain, it finds the free RDTE
     on the chain.  Results can vary based on the
     state of the storage where the RDTE had been.
     This could be a loop in ISTTSCWU, an ABEND0C4
     in ISTTSCWU, an ABEND0A9 in ISTCPCDR, or just
     CPRC recorded in the VIT in ISTCPCDR.
  

Problem conclusion

• The following changes have been made:
  ISTLUCST and ISTSSCU3 have been changed to make
  the RDTE not findable when adding the RDTE to
  the TSEXT_TN_RDTES chain.
  DYNAMRDT, ISTCPCDR, ISTTSCWU, ISTDECL2, ISTOCCMV,
  ISTPUCOA, and ISTTSCWU have been changed to pass
  the RDTE at the appropriate times.
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

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

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

  UA61985 UA61986

Modules/Macros

• DYNAMRDT ISTCPCDR ISTDECL2 ISTLUCST ISTOCCMV
  ISTPUCOA ISTSSCU3 ISTTSCWU
  

Fix information

• Fixed component name

  VTAM V4 MVS/ESA

• Fixed component ID

  569511701

Applicable component levels

• R1C0 PSY UA62075

     UP11/12/21 P F112

• R1D0 PSY UA62076

     UP11/12/21 P F112

Fix is available

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