PI18455: MAXSOCKET LIMIT WHEN SOCKET POOLING USED IN CICS

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• You see a large increase in the number of sockets being used.
  The AF_INET socket usage might increase to over 90%.
  It may hit the MAXSOCKET limit.
    The biggest contributor is:   DFHKETCB
  A look at a CICS region's
          Number of open files for this process:
  may exceed 15,000 and still be growing.
  .
    A dump of the CICS region,
  in the SO (sockets) domain,
  under the    ===SO: SOCKETS DOMAIN - SUMMARY
          Owned Sockets:
  might show a large number of sockets, as seen above.
  .
  But, the tokens and other information for each socket is zeros,
  except the number of tasks that have been involved with it.
  For example:
  ---------------------------------------------------------------
  TOKEN    FLAGS  Send ECB Recv ECB I/O   Dom  Gate Remote
  00000000        00000000 00000000          0    0
  .
     IPAddr        Port  Task
                     0    1
  ---------------------------------------------------------------
  .
    The problem is caused by a WEB-OPEN request in a CICS task.
  This causes a SOCKET create to be issued.
    When SOCKET pooling is used
  the CICS SOCKET TOKEN does not get re-used.
    So after many thousands of WEB OPEN requests
  all the SOCKET token get used
  and there is none on the FREE chain.
    From that point on, the next WEB OPEN will cause
  a SOCKET to be obtain from TCPIP via the SOCK CREATE.
  This returns a SOCK TOKEN of 0.
    DFHWBCL then does a SOCKET CONNECT passing the SOCKET token.
  The CONNECT failed because the token is 0.
    WBCL then tries to tidy up by doing a SOCKET CLOSE.
  This also fails, resulting in the SOCKET being orphaned.
  After a while, all the SOCKETs in TCPIP will get consumed.
  .
  Additional keywords: DFHWB0002 (code X'0B08') DFHWBSO
  followed by DFHSO0114
  KIXREVxxx
  

Local fix

• Do not use SOCKET Pooling until this problem has been resolved.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: CICS TCP/IP socket usage continually    *
  *                      grows when using HTTP outbound          *
  *                      connection pooling.                     *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  CICS is using outbound HTTP connection pooling.  When a socket
  is removed from the pool to be reused the state of the
  connection is checked to ensure it is still active.  If the
  connection has now been closed by the remote system the socket
  is closed by CICS and the CICS control blocks freed.
  
  As part of this process DFHSOMG should set the current socket
  token to be unused. DFHSOMG is specifying an incorrect value for
  the socket token. This leaves the actual socket token still
  marked as in use. A new socket is created and it gets allocated
  the next available token.
  
  Eventually all possible socket tokens are marked as allocated
  and DFHSOMG allocates a token of 0 to all future sockets.
  This token is invalid and the caller is unable to perform any
  socket functions using this token.  This means that the caller
  is unable to indicate that the socket should be closed.  The
  socket control blocks and the actual TCP/IP socket are never
  freed.
  
  Over time the CICS region can end up at the MAXSOCKETS limit
  even though no (or very few) sockets are actually in use.
  

Problem conclusion

• DFHSOMG has been changed to release the correct socket token
  when closing a pooled socket.
  

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:

  PI19090 UI19503 UI19504

Modules/Macros

• DFHSOAD  DFHSOCK  DFHSODM  DFHSODUF DFHSOIS  DFHSOLI  DFHSOLS
  DFHSOLX  DFHSOL   DFHSOM01 DFHSOM02 DFHSOM03 DFHSOPL  DFHSORD
  DFHSOS00 DFHSOS01 DFHSOS02 DFHSOS03 DFHSOS04 DFHSOS05 DFHSOS06
  DFHSOS07 DFHSOS08 DFHSOS09 DFHSOS10 DFHSOS11 DFHSOS12 DFHSOS13
  DFHSOS14 DFHSOS15 DFHSOS16 DFHSOS17 DFHSOS18 DFHSOS19 DFHSOS20
  DFHSOS21 DFHSOS22 DFHSOS23 DFHSOSE  DFHSOST  DFHSOTB  DFHSOTI
  DFHSOTRI DFHSOUE  DFHSOXM
  

Fix information

• Fixed component name

  CICS TS Z/OS V5

• Fixed component ID

  5655Y0400

Applicable component levels

• R800 PSY UI19504

     UP14/07/17 P F407

• R900 PSY UI19503

     UP14/07/17 P F407

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.