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OA36401: ABEND0C4 AT X'F24' INTO ISTTSCND

A fix is available

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APAR status

  • Closed as program error.

Error description

  • When the ABEND0C4 occurs, the instruction at x'F24' into
    ISTTSCND is attempting to load the halfword value
    AUNCB_XID_MAXPIU into GPR7, using the value in GPR5
    as the base register for the control block supposedly containing
    the field AUNCB_XID_MAXPIU, which is at offset x'3A6' into the
    AUNCB.   The problem is that GPR5 points to an AHNCB, not an
    AUNCB, and an AHNCB is only x'1F8' bytes long.   Therefore,
    since offset x'3a6' is past the end of that AHNCB, the ABEND0C4
    results when the load instruction is executed.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All using Enterprise Extender connections.   *
    ****************************************************************
    * PROBLEM DESCRIPTION: ABEND0C4 occurs in module               *
    *                      ISTTSCND immediately after a            *
    *                      path switch.                            *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    Sample Configuration:
    
         <-------CNR00005------->
    --------                  --------
    -      - =======EE======= -      -
    -VTAM A-                  -VTAM B-
    -      - ======AHHC====== -      -
    --------                  --------
    
    
    The problem is summarized as follows:
    
    1) An HPR pipe is established between VTAM A to VTAM B
       over an EE connection.
    2) VTAM A transmits a packet over CNR00005 to VTAM B.
    3) As data is transmitted from RTP, the TSCB_RPNCB
       field is filled in by the local RTP endpoint with the
       internal address of the RPNCB control block.
    4) The TSCB is built and forwarded to the EE TCP/IP
       stack for transmission.
    5) While the TCP/IP stack is sending the HPR
       packet, VTAM B initiates and completes a path
       switch for this pipe.
    6) At this point, the HPR pipe path switched from an EE
       connection to an AHHC connection.
    7) On VTAM A, the outstanding HPR packet is returned
       to VTAM from the EE TCP/IP stack.
    8) Module ISTTSCND processed the packet and located the
       RPNCB control block from the TSCB_RPNCB field.
    9) Segment CHECKMTU, is referencing various AUNCB fields
       (i.e. AUNCB_MTU_SIZE, AUNCB_XID_MAXPIU) which are associated
       with EE connections.
    10) The AUNCB is based on the RPNCB_LOCAL_NCB_PTR.  The
       RPNCB_LOCAL_NCB_PTR is now pointing to an AHNCB control block
    11) The AHNCB represents the AHHC connection.  Since the AHNCB
       is not as large as the AUNCB, an ABEND0C4 occurred when
       referencing these fields.
    

Problem conclusion

  • ISTTSCND - Corrected segment CHECKMTU to verify the
               RPNCB_LOCAL_NCB_PTR is still referencing an AUNCB
               control block when a packet is returned back to VTAM.
    ISTAUCLA - Included for maintenance purposes.
    

Temporary fix

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

Comments

APAR Information

  • APAR number

    OA36401

  • Reported component name

    VTAM V4 MVS/ESA

  • Reported component ID

    569511701

  • Reported release

    1C0

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2011-05-04

  • Closed date

    2011-05-18

  • Last modified date

    2011-08-01

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

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

    UA60444 UA60445

Modules/Macros

  • ISTAUCLA ISTTSCND
    

Fix information

  • Fixed component name

    VTAM V4 MVS/ESA

  • Fixed component ID

    569511701

Applicable component levels

  • R1C0 PSY UA60444

       UP11/07/06 P F107 Ž

  • R1D0 PSY UA60445

       UP11/07/06 P F107 Ž

Fix is available

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Document Information

Modified date:
01 August 2011