今天在检查alert.log日志时，发现了一个错误号：ORA-3136 WARNING: inbound connection timed out

查了一下metalink，原因如下：(参考DOC_ID:793259.1, 465043.1)
    The "WARNING: inbound connection timed out (ORA-3136)" in the alert log indicates that the client was not able to complete  it's authentication within the period of time specified by parameter SQLNET.INBOUND_CONNECT_TIMEOUT. 
    The most common reason for warning message in alert log is when an user gets error at connect time, ORA-01017 invalid username /password , and on the same prompt, if no update is made for 1 minute(default) then the alert loggets WARNING: inbound connection timed out (ORA-3136)
    重现异常：
    1. SQLNET.INBOUND_CONNECT_TIMEOUT=60(default value) 
    将SQLNET.INBOUND_CONNECT_TIMEOUT=5 添加到$ORACLE_HOME/network/admin/sqlnet.ora中，表示以5秒钟为检测单位
  2.tnsname.ora中添加服务名进去
    nfdb=
       (DESCRIPTION=
              (ADDRESS=(HOST=172.16.203.198)(PORT=1521)(PROTOCOL=TCP))
              (CONNECT_DATA=
              (SERVER=DEDICATED)
              (SERVICE_NAME=nfdb)
               )
       )
  3.sqlplus session and enter wrong username or password
    $ sqlplus system/jkkdsf@nfdb
    SQL*Plus: Release 10.2.0.3.0 - Production on Thu Mar 19 17:51:35 2009
    Copyright (c) 1982, 2006, Oracle. All Rights Reserved.
    ERROR:
    ORA-01017: invalid username/password; logon denied
  4.Keep the sqlplus session open for 5 seconds and in the alert log after 5th second , you will notice ORA-3136
    $tail -f alert_nfdb.log
     Thu Mar 19 17:52:36 2009
     WARNING: inbound connection timed out (ORA-3136)
     note:如果没有满足参数SQLNET.INBOUND_CONNECT_TIMEOUT退出了sql>连接，那么此时就不会遇到这个错误。