PK73554: LOTS OF SOCKETS ON A CICS SYSTEM

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• It seems there is a further small timing window where the alias
  task and CSOL can both be relinquishing use of the socket at
  at the same time.  This timing window  causes neither task to
  close the socket and leaves it 'hanging' .
  
    The timing window occurs when both tasks enter relinquish_lt
  processing and CSOL obtains the exclusive lock first.  CSOL goes
  through relinquish_lt believing that the alias task will close
  the socket.
  The alias task has got through most of its checks unaware of
  CSOL's interest in the socket and so assumes that the socket
  is to remain active.
  PK60993 addressed the problem caused by a much larger timing
  window but this race for the exclusive could still occur.
  Addtional Keywords: CLOSEWAIT, CLOSWAIT
  

Local fix

• NO
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All                                          *
  ****************************************************************
  * PROBLEM DESCRIPTION: Build up of sockets can lead to         *
  *                      MAXSOCKETS condition.                   *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  CSOL is performing a notify for the close of a socket which has
  been requested by the client. At the same time the alias task
  is terminating and issues sock_perform_commit. Both CSOL and the
  alias transaction will close and delete the socket if there are
  no other active users, but due to a specific timing scenario,
  neither of them do and the socket is left open with no-one left
  to close it. The TCPIPSERVICE then cannot be closed.
  The problem will occur if the web alias task enters socket
  relinquish processing just ahead of CSOL but loses control
  of the processor before obtaining the SOLTLOCK. CSOL overtakes
  the web alias task and completes relinquish processing.
  CSOL is told not to close and delete the socket because the
  web-alias task still has a reserve on the socket.
  The web-alias task now completes relinquish processing but it
  also bypasses logic to close and delete the socket because the
  socket was in use when relinquish processing commenced.
  
  ADDITIONAL KEYWORDS :- SOCK_REL
  

Problem conclusion

• CICS has been changed so that a relinquish lock is
  used in relinquish processing to force single threading.
  

Temporary fix

• FIX AVAILABLE BY PTF ONLY
  

Comments

APAR Information

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

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

  UK43796 UK43797

Modules/Macros

•    DESSOCK  DESSODM  DESSODUF DESSOIS  DESSOLS
  DESSOLT  DESSOMG  DESSOSO  DESSOUS  DFHSOCK  DFHSODM  DFHSODUF
  DFHSOIS  DFHSOLS  DFHSOLTC 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 DFHSOUSC
  

Fix information

• Fixed component name

  CICSTS V3 Z/OS

• Fixed component ID

  5655M1500

Applicable component levels

• R400 PSY UK43796

     UP09/02/07 P F902

• R500 PSY UK43797

     UP09/02/07 P F902

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.