PQ68544: TCPIP CICS LISTENER LOOPS ON RECEIVE WHEN PEEKING DATA WHEN LESSDATA SENT THEN CONFIGURED OR CONNECTION CLOSED BY CLIENT.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• If the TCPIP CICS Listener is configured to receive a certain
  amount of data it is to peek when less is sent by the client
  the Listener will loop on its Receive Peek option. If the client
  connection is closed the loop persists since the receive never
  completes; so the lesser amount of data is not really read. Thus
  a receive of zero length is never seen.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of the IBM Communications Server   *
  *                 for z/OS Version 1 Releases 2 & 4 IP:        *
  *                 CICS Sockets                                 *
  ****************************************************************
  * PROBLEM DESCRIPTION: High CPU utilization when a client      *
  *                      sends incomplete data to an enhanced    *
  *                      CICS listener that is configured with   *
  *                      the PEEKDAT=YES option                  *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  An enhanced CICS listener has been configured with YES specified
  as the PEEKDATa parameter and a positive value specified as the
  MSGLENth parameter.
  A remote client connects to the listener and sends data whose
  length is less than the MSGLEN value.  Since PEEKDAT=YES, the
  listener receives the data using the PEEK option.  This means
  that the data remains queued waiting to be received.  The
  listener sees that the data length is less than MSGLEN and
  therefore immediately issues another RECV (with the PEEK option)
  to get the remainder of the data.  Since the same data is still
  waiting to be received (because the PEEK option was used on the
  previous RECV), the RECV completes immediately with the same
  result.  Hence, the listener loops issuing the RECV over and
  over until the client sends in the remainder of the data.  If
  the client closes its socket before sending the remainder of the
  data, then the loop continues indefinitely.
  +-------------------------------------------------------------+
  + Please check our Communications Server for OS/390 homepages +
  + for common networking tips and fixes.  The URL for these    +
  + homepages can be found in Informational APAR II11334.       +
  +-------------------------------------------------------------+
  

Problem conclusion

• The CICS Sockets listener program, EZACIC02, has been amended to
  properly manage the situation where a client sends incomplete
  data to an enhanced listener that is configured with the
  PEEKDAT=YES option.  EZACIC02 has also been amended to detect
  when the client closes its socket.
  
  The following change to message EZY1301E needs to be added to
  these manuals:
  
  z/OS IBM Communications Server
  IP CICS Sockets Guide
  Version 1 Release 2
  Document Number SC31-8807-00
  
  z/OS IBM Communications Server
  IP Messages:
  Volume 3 (EZY)
  Version 1 Release 2
  Document Number SC31-8785-01
  
  z/OS IBM Communications Server
  IP CICS Sockets Guide
  Version 1 Release 4
  Document Number SC31-8807-01
  
  z/OS IBM Communications Server
  IP Messages:
  Volume 3 (EZY)
  Version 1 Release 4
  Document Number SC31-8785-02
  
  EZY1301E mm/dd/yy hh:mm:ss CONNECTION CLOSED BY CLIENT
  TRANSACTION= transactionid PARTNER INET ADDR= ipaddr
  PORT= port
  
  EXPLANATION: A remote client connected to the CICS Listener but
  then closed the connection before sending the entire amount of
  data required by the Listener as determined by the MINMSGL
  standard Listener configuration parameter or the MSGLEN
  enhanced Listener configuration parameter.
  
  mm/dd/yy is the date (month/day/year) of the message.
  
  hh:mm:ss is the time (hours:minutes:seconds) of the message.
  
  transactionid is the transaction name of the CICS Listener.
  
  ipaddr is the internet address of the remote client.
  
  port is the port number of the remote client.
  
  SYSTEM ACTION: Listener transaction transactionid continues.
  
  USER OR OPERATOR RESPONSE: Correct the client program.
  
  SYSTEM PROGRAMMER RESPONSE: None.
  
  SOURCE DATA SET: EZACIC02
  
  PROCEDURE NAME: LISTENER
  
  
  * Cross Reference between External and Internal Names
  

Temporary fix

Comments

APAR Information

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

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

  UQ72818 UQ72819

Modules/Macros

• EZACICME EZACIC02
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R120 PSY UQ72818

     UP03/01/10 P F301

• R140 PSY UQ72819

     UP03/01/10 P F301

Fix is available

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