2072947 - DB6: First steps for troubleshooting SQL30081N Communication errors

• Short dumps in ST22 showing something like:
  ST22:
  Runtime Errors         DBIF_RSQL_SQL_ERROR
  Exception              CX_SY_OPEN_SQL_DB
  Date and Time          -----------------

  Short text
      SQL error in the database when accessing a table.

  How to correct the error
      Database error text........: "SQL30081N A communication error has
  been  detected. Communication protocol being used: "TCP/IP".
  Communication API being used: "SOCKETS". Location where the error was
  detected: "xxx.xxx.xxx.xxx".
      Communication function detecting the error: "recv". Prot"
      Internal call code.........: "[RSQL/READ/KNA1 ]"
      Please check the entries in the system log (Transaction SM21).

• Entries in the syslog (transation SM21) like:

  03:11:29 BTC 044 Database error -30081 at CON
  03:11:29 BTC 044 > SQL30081N A communication error has been detected.
  03:11:29 BTC 044 > Communication protocol being used: "TCP/IP".Communication
  03:11:29 BTC 044 > API being used: "SOCKETS". Location where the error was
  03:11:29 BTC 044 > detected: "xxx.xxx.xxx.xxx". Communication functiondetecting
  03:11:29 BTC 044 > the error: "selectForRecvTimeout". Protocol specific error
  03:11:29 BTC 044 > code(s): "10054", "*", "*". SQLSTATE=08001
  03:11:29 BTC 044 Database error -30081

• Developer traces:

  Entries in dev_wX.log such us:

  C  *** ERROR in DB6Connect[dbdb6.c, 1798] CON = 1 (BEGIN)
  C  &+     DbSlConnectDB6( SQLConnect ): [IBM][CLI Driver] SQL30081N  A communication error has been detected. Communication
  C  &+     protocol being used: "TCP/IP".  Communication API being used:"SOCKETS".  Location where the error was detected: "
  C  &+     xxx.xxx.xxx.xxx".  Communication function detecting the error:
  C  &+     xxx.xxx.xxx.xxx".  Communication function detecting the error: "recv".  Protocol specific error code(s): "10054", "*
  C  &+     ", "0".  SQLSTATE=08001                                                                                          
  C  &+
  C  &+
  C  &+     ABAP location info 'CL_SQL_CONNECTION=============CP', 337
  C  &+
  C  *** ERROR in DB6Connect[dbdb6.c, 1798] (END)
  C  *** ERROR => DbSlConnect to '<SID>' as 'DB2<SID>' failed [dbdb6.c      1811]

• SAP system on IBM Db2 for Linux, UNIX and Windows

SQL30081N, selectForRecvTimeout, "recv", NUM_LOG_SPAN , KBA , BC-DB-DB6 , DB2 Universal Database for Unix / NT , How To