PH44270: IMPROVED DETECTION AND REMOVAL OF INCOMPLETE CONNECTIONS TO DB2

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• Many DBATs in "028.DBAA 05" or "028.DBAT 02" waiting for
  distributed clients to complete connection setup and DBATs
  cannot be used by any other connection.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All Db2 for z/OS Distributed Data Facility                   *
  * (DDF) Users.                                                 *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * Db2 -DISPLAY THREAD command shows                            *
  * many DBATs with IDs of "028.DBAA  02"                        *
  * or "028.DBAA  05"                                            *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  When a distributed client using TCP/IP requests a DRDA
  connection to Db2, Db2 schedules a DBAT to process the
  connection request. To complete a DRDA connection, a client
  must exchange with Db2 4 DRDA message objects which identify
  the client type and a user with its security credentials.
  These exchanges can be accomplished by the client sending
  anywhere from 1 to 4 TCP/IP network messages. However, if
  the client connection does not complete the processing of the
  required DRDA message flows, the DBAT assigned to handle the
  connection processing cannot be used for any other client
  request. When a Db2 -DISPLAY THREAD command is issued, many
  threads will be displayed showing a NAME value of the
  subsystem-id and an ID value of "028.DBAA  02" or a NAME
  value of "DISCN-NC" and an ID value of "028.DBAA  05". Also
  a -STOP DB2 or DDF MODE(QUIESCE) command will not complete
  which may require a -STOP DB2 or DDF MODE(FORCE) command to
  complete Db2 or DDF termination.
  

Problem conclusion

Temporary fix

Comments

• Db2 has been changed to detect and terminate TCP/IP client
  connections that have not completed the necessary DRDA
  message flows by utilizing TCP/IP synchronous receives with
  5 second receive timeout values. When a TCP/IP synchronous
  receive times out, Db2 will consider the client connection
  as incomplete and terminate the connection. Db2 will then
  attempt to issue new message DSNL079I to display the number
  of terminations of incomplete connections that have so far
  been performed. Note, the new message DSNL079I is on a 5
  minute interval timer, such that the message may not appear
  at the same time as an incomplete connection was terminated.
  To provide information as to which clients had incomplete
  connection terminations, the -DISPLAY LOCATION command has
  been enhanced with a new option, INCOMPLT, which is mutually
  exclusive with the DETAIL option. The output from the
  -DISPLAY LOCATION INCOMPLT command will list all client
  locations with the number of client connections from the
  client location that had incomplete connections terminated
  since DDF was started.
  Db2 will also increment the number of client connections
  terminated by Db2 in the QLSTCNVT field of the IFCID365
  locations statistics entry for the particular remote
  location as well as the QLSTCNVT field of the
  DRDA REMOTE LOCS statistics data produced during a normal
  Db2 statistics trace interval.
  Refer to this APAR's ++HOLD DOC for details on the new
  Db2 message, DSNL079I, an update to the -DISPLAY LOCATION
  command, and an update to the explanation
  of the existing QLSTCNVT field of location statistics.
  

APAR Information

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

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

  UI79763

Modules/Macros

• DSNDQLST DSNLIRTR DSN9SCNA DSNFLDIR DSN@QLST DSNLEDDA DSNFCDIR
  DSNLDL
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RC10 PSY UI79763

     UP22/03/24 P F203

Fix is available

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