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PM37810: DFHSO0002 CODE X'0206' IN MODULE DFHSOCK FOLLOWED SHORTLY BY DFHSO0126 CREATING A SOCKET FAILS DUE TO MAXSOCKETS LIMIT HIT.

A fix is available

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APAR status

  • Closed as unreproducible.

Error description

  • Having intermittent issues with the socket interface, the
    following message appears:
    .
    +DFHSO0002 REGNNAME A severe error (code X'0206') has occurred
    in module DFHSOCK
    .
    Soon after, the ability to use the interface stops and the
    following message comes out repeatedly:
    .
    +DFHSO0126 W REGNNAME An attempt to create a socket has failed
    because the MAXSOCKETS limit has been reached.
    .
    To temporarily resolve the issue you can Stop and then Start the
    TCPIPSERVICE.
    .
    The TASK suffering the DFHSO0002 is CSOL, below is the Kernel
    Stack for CSOL:
    .
     OFFSET ERR NAME
     0003BC     DFHKETA
     000218     DFHDSKE
     0011CC     DFHXMTA
     000FBA     DFHPGPG
     000192     INITIAL_LINK
     000000     DFHAPLI1
     000AAC     CICS_INTERFACE
     003E70     DFHSOLS
     0001BC     LISTEN_SOLS
     00202E     ACCEPTED_CONNECTION
    .
    ACCEPTED_CONNECTION - calls get_exc_lock gets SOLOCK
    .
     000A56     DFHSOM01
    .
    DFHSOM01 - called to add lock, but at max.. so calls DFHSOCK
    to close
    .
     004E72     DFHSOCK
    .
    DFHSOCK - tries to get the SOLOCK again causing the error below
    .
     000282     CLOSE_SOCK
     002076     GET_EXC_LOCK
     004F22     SEVERE_ERROR
     003C64     DFHMEME
     000266     SEND
     0032F8     CONTINUE_SEND
     001578     TAKE_A_DUMP_FOR_CALLER
     001504     DFHDUDU
     000200     SYSTEM_DUMP
     000F54     TAKE_SYSTEM_DUMP
    .
    Looking in the SO Domain you can see they are at MAXSOCKETs
    .
    Current MaxSockets:    255
    HardLimit MaxSockets:    512
    Owned Sockets:     254
    .
    Then after this problem occurs they see continous DFHSO0126
    messages.
    .
    In the Internal Trace you'll see the following entries:
    .
    SO 0E02 SOUS  *EXC* - ASYNCIO_ERROR RETURN_VALUE(1)
                          RETURN_CODE(0)
                          REASON_CODE(00000000)
    .
    SO 0206 SOCK  *EXC* - LOCK_ERROR
    .
    When maxsocket has been reached, the CSOL task will attempt to
    close sockets that are unused when a new request from a client
    is received. Part of DFHSOCK CLOSE is to obtain an exclusive
    LOCK for SOLOCK. However, the SOLOCK has already been obtain
    earlier by CSOL causing the resulting in the LOCK_ERROR see in
    the trace and the SO0002 SDUMP.
    .
    You may also see the following message as well in some
    instances:
    .
    DFHSO0001 An abend (code ---/ASOB) has occurred at offset
              X'0956' in module DFHSOM02.
    .
    Additional Symptom(s) Search Keyword(s):
    KIXREVDAM
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All CICS users.                              *
    ****************************************************************
    * PROBLEM DESCRIPTION: Active IPIC connection is released      *
    *                      when maxsocket condition is exceeded.   *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    When MAX socket condition reached.
    CICS will free a dead unowned socket
    for use. If there is no dead socket,
    first socket in unowned socket chain
    will be chosen. If there is IPIC
    connection. It will be chosen and
    closed even if it is active. It will
    leads to IPIC connection released and
    succeeding async_io error by IPIC
    connection.
    

Problem conclusion

Temporary fix

  • FIX AVAILABLE BY PTF ONLY
    

Comments

  • DFHSOM01 has been changed to not choose first unowned socket if
    no dead socket found.
    

APAR Information

  • APAR number

    PM37810

  • Reported component name

    CICSTS V3 Z/OS

  • Reported component ID

    5655M1500

  • Reported release

    500

  • Status

    CLOSED UR3

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2011-04-26

  • Closed date

    2011-08-11

  • Last modified date

    2011-09-01

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

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

    UK70721

Modules/Macros

  •    DESSOMG  DESSOSO  DFHSOMGC DFHSOM01 DFHSOM02
    DFHSOM03 DFHSOSOC DFHSOS00 DFHSOS01 DFHSOS02 DFHSOS03 DFHSOS04
    DFHSOS05 DFHSOS06 DFHSOS07 DFHSOS08 DFHSOS09 DFHSOS10 DFHSOS11
    DFHSOS12 DFHSOS13 DFHSOS14 DFHSOS15 DFHSOS16 DFHSOS17 DFHSOS18
    DFHSOS19 DFHSOS20 DFHSOS21 DFHSOS22 DFHSOS23
    

Fix information

  • Fixed component name

    CICSTS V3 Z/OS

  • Fixed component ID

    5655M1500

Applicable component levels

  • R500 PSY UK70721

       UP11/08/16 P F108

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.

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Document Information

Modified date:
01 September 2011