PK15713: AFTER APPLYING PTF UK06950 CUSTOMER STARTS RECEIVING REPEATED DFHSO0126 MESSAGES INDICATING MAXSOCKETS H 05/10/04 PTF PECHANGE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• After applying PTF UK06950 message DFHSO0126 starts coming out
  repeatedly stating:  "An attempt to create a socket has failed
  because the MAXSOCKETS limit has been reached."
  .
  This problem is exposed by PTF UK06950 which added code to
  repeat an earlier test which checks the validity of the socket
  token during socket close processing.
  .
  This test should have been an exact repeat of the earlier test.
  However, this test checks the DFHSOCK parameter list to see if
  a socket token has been passed by the caller. During end-of-task
  syncpoint, DFHSOCK creates a pseudo parameter list in
  sock_rmc_close_on_relinquish for function CLOSE (to close the
  socket). Initially, this is primed with a socket token which is
  why the first test to validate the socket token works.
  .
  However, the parameter list is in storage which is shared with
  other domain calls. If the task loses control on the SOLOCK
  during socket close processing, the socket token in the DFHSOCK
  parameter list gets wiped out by the DFHLMLM lock manager call
  (which shares the same parameter list storage). This will cause
  the second attempt to validate the socket token to fail which
  causes ?close_sock to skip the final deletion of the socket as
  code added by UK06950 thinks that another task has beaten us to
  it.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS Users with PK10559 applied.         *
  ****************************************************************
  * PROBLEM DESCRIPTION: MSGDFHSO0126 repeatedly issued due to   *
  *                      unexpected MAXSOCKETS condition.        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  After applying PK10559, message DFHSO0126 is issued repeatedly
  after a period of HTTP or ECI over TCPIP activity.
  Inbound HTTP sockets and ECI over TCPIP sockets are normally
  closed and deleted by DFHSOCK PERFORM_COMMIT processing. This
  happens when the last task to reference the socket terminates
  and there is no send or receive activity against the socket.
  DFHSOCK sets up a temporary parameter list containing the
  socket token to be closed and deleted before calling routine
  Close_sock.
  Close_sock was changed by PK10559 to verify that the socket
  token was still valid just before deleting it.
  The verify routine can return a negative response even though
  the socket still exists. This can arise because the parameter
  list used by DFHSOCK to hold the socket token is a shared
  parameter list which is used for other things such as lock
  manager calls.
  If routine Close_sock loses control on the SOLOCK, the reference
  to the socket token is lost and the socket object will not be
  deleted.
  If this situation occurs frequently, it can lead to a MAXSOCKETS
  condition. This causes new socket connections to be rejected
  with message DFHSO0126.
  

Problem conclusion

• UK06950
  DFHSOCK has been changed so that the parameter list containing
  the socket token passed to close_sock is no longer shared.
  

Temporary fix

•             *********
              * HIPER *
              *********
  FIX AVAILABLE BY PTF ONLY
  

Comments

APAR Information

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

  PK12826

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

  UK09548

Modules/Macros

•    DESSOCK  DFHSOCK
  

Fix information

• Fixed component name

  CICSTS 3.1 Z/OS

• Fixed component ID

  5655M1500

Applicable component levels

• R400 PSY UK09548

     UP05/12/02 P F512 ®

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.