PK60993: CEMT SET TCPIPSERVICE(NAME) CLOSED MAY HANG IN BEING CLOSED STATUS.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• You issue a CEMT SET TCPIPSERVICE(name) CLOSED command and
  sometimes it hangs in BEING CLOSED status and the TCPIPSERVICE
  never closes.
  
  A DFHTRAP was written and the following problem was found.
  The trace shows this socket being created and being closed by
  the client but it never gets deleted by CICS.  Task-01070 is
  the CWXN task attached when this new socket is created.
  Task-01071 is the web-alias task which CWXN attaches.  After
  Task-01071 sends its response to the client, it issues an
  ASYNC receive to accept the next request from the client.
  Almost immediately after this, the socket listener task gets
  notified that the client has closed the connection (this can
  only happen after an ASYNC RECEIVE has been issued).  DFHWBSO
  is called for SOCKET_CLOSED for the socket.  In parallel with
  this, TASK-01071 starts to go through DFHSOCK PERFORM_COMMIT
  logic.  Code in DFHSOCK PERFORM_COMMIT checks the state of
  this socket.  At this point notify_count is non-zero
  (incremented by CSOL - TASK-00004 as part of notify
  processing).  TASK-01071 therefore deems the socket to be in-
  use.  This causes DFHSOCK PERFORM_COMMIT to eventually bypass
  its own socket close logic which exists for deleting inactive
  sockets.  Before TASK-01071 can relinquish its reserve on the
  socket, TASK-00004 issues its own relinquish. Relinquish
  logic returns a doclose flag which is only set if there are
  no other reserves on the socket.  Relinquish returns doclose=
  no to TASK-00004 (as TASK-00071 still has a reserve).  So
  TASK-00004 decides that the socket is still active and skips
  close processing for the socket.  It expects the task which
  currently holds a reserve on the socket (TASK-01071) to
  eventually close and delete it the socket.  This will not
  happen as explained earlier.  So both CSOL and the web-alias
  task go through logic which will delete the socket if it is
  deemed to be inactive but both tasks note the presence of the
  other and assume that the other task will do the close.  CICS
  needs to ensure that one of these 2 tasks closes and deletes
  the socket when this timing clash occurs.
  
  Additional Symptom(s) Search Keyword(s):
  KIXREVSCB
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All.                                         *
  ****************************************************************
  * PROBLEM DESCRIPTION: CEMT SET TCPIPSERVICE() CLOSED hangs    *
  *                      in BEING CLOSED.                        *
  ****************************************************************
  * 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 alias transaction checks the
  notify_count flag in sock_perform_commit before CSOL has
  decremented it. It will then set the curr_in_use flag on to
  indicate that a notify task is still using the socket.
  If CSOL then gets control and relinquishes the socket, CSOL will
  detect that the alias task still has a reserve on the socket
  and so will not close and delete the socket.
  When the alias task then performs a relinquish of the socket, it
  should carry on to delete the socket, as CSOL has already
  relinquished the socket. But because the curr_in_use flag is set
  it thinks that the socket is still in use by a notify task and
  does not close / delete the socket either.
  

Problem conclusion

• DFHSOCK has been modified in perform_commit processing to
  check for the presence of a notify task using the socket, which
  could prevent closure of the socket, only after the relinquish
  socket call has been made by the terminating task.
  

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:

  UK37671 UK37672

Modules/Macros

•    DESSOCK  DFHSOCK
  

Fix information

• Fixed component name

  CICSTS V3 Z/OS

• Fixed component ID

  5655M1500

Applicable component levels

• R400 PSY UK37671

     UP08/07/01 P F806

• R500 PSY UK37672

     UP08/07/01 P F806

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.