收到报警，检查alert文件，发现以下wainning：
Fatal NI connect error 12170.
VERSION INFORMATION:
TNS for Linux: Version 11.2.0.4.0 - Production
Oracle Bequeath NT Protocol Adapter for Linux: Version 11.2.0.4.0 - Production
TCP/IP NT Protocol Adapter for Linux: Version 11.2.0.4.0 - Production
Time: 13-JUL-2017 13:22:00
Tracing not turned on.
Tns error struct:
ns main err code: 12535
TNS-12535: TNS:operation timed out
ns secondary err code: 12606
nt main err code: 0
nt secondary err code: 0
nt OS err code: 0
Client address: (ADDRESS=(PROTOCOL=tcp)(HOST=10.205.53.12)(PORT=23730))
WARNING: inbound connection timed out (ORA-3136)
有三种因素会导致这个警告出现：
1.Server gets a connection request from a malicious client which is not supposed to connect to the database , in which case the error thrown is the correct behavior. You can get the client address for which the error was thrown via sqlnet log file.
2.The server receives a valid client connection request but the client takes a long time to authenticate more than the default 60 seconds.
3.The DB server is heavily loaded due to which it cannot finish the client logon within the timeout specified。
第1种可以通过sqlnet.log($ORACLE_HOME/network/log/下)文件确定，第3种可以用top -c查看DB Server的load来确定。
下面再现第2种可能：
通过oracle 11gr2 client 连接db，然后故意输入错误的账号密码，等待60秒钟，检查alert日志文件就可以看到这种warning了。
C:\Users\mdu>sqlplus [email protected]
SQL*Plus: Release 11.2.0.1.0 Production on 星期六 1月 19 13:58:11 2013
Copyright (c) 1982, 2010, Oracle. All rights reserved.
输入口令:
连接到:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning, Real Application Clusters, Automatic Storage Management,
Data Mining and Real Application Testing options
SQL> conn [email protected] ###输入错误的用户名及密码
输入口令:
ERROR:
ORA-01017: invalid username/password; logon denied
警告: 您不再连接到 ORACLE。
SQL> ####此session等待60秒钟不再做任何操作
[email protected]$ tail -20 alert_CHNPELT1.log
***********************************************************************
Fatal NI connect error 12170.
VERSION INFORMATION:
TNS for Linux: Version 11.2.0.2.0 - Production
Oracle Bequeath NT Protocol Adapter for Linux: Version 11.2.0.2.0 - Production
TCP/IP NT Protocol Adapter for Linux: Version 11.2.0.2.0 - Production
Time: 19-JAN-2013 13:59:41
Tracing not turned on.
Tns error struct:
ns main err code: 12535
TNS-12535: TNS:operation timed out
ns secondary err code: 12606
nt main err code: 0
nt secondary err code: 0
nt OS err code: 0
Client address: (ADDRESS=(PROTOCOL=tcp)(HOST=10.64.108.62)(PORT=60809))
WARNING: inbound connection timed out (ORA-3136)
我们发现，已经再现成功了。
为什么要等待60秒钟呢？
因为在sqlnet.ora文件中有一个默认的参数SQLNET.INBOUND_CONNECT_TIMEOUT来控制这个时间，如果没有显式的指定此参数，那么默认就是60秒钟。
如果不想在alert日志中收到这样的报错，可以设置SQLNET.INBOUND_CONNECT_TIMEOUT=0.
下面是从网上搜索的关于SQLNET.INBOUND_CONNECT_TIMEOUT的介绍：
Question: What is the "sqlnet.inbound_connect_timeout" parameter and how do I use sqlnet.inbound_connect_timeout for logging off idle sessions?
Answer: The sqlnet.inbound_connect_timeout parameter is used to limit the time, set in seconds, for a client to connect with the database server and provide the required authentication information.
---恢复内容结束---
收到报警，检查alert文件，发现以下wainning：
Fatal NI connect error 12170.
VERSION INFORMATION:
TNS for Linux: Version 11.2.0.4.0 - Production
Oracle Bequeath NT Protocol Adapter for Linux: Version 11.2.0.4.0 - Production
TCP/IP NT Protocol Adapter for Linux: Version 11.2.0.4.0 - Production
Time: 13-JUL-2017 13:22:00
Tracing not turned on.
Tns error struct:
ns main err code: 12535
TNS-12535: TNS:operation timed out
ns secondary err code: 12606
nt main err code: 0
nt secondary err code: 0
nt OS err code: 0
Client address: (ADDRESS=(PROTOCOL=tcp)(HOST=10.205.53.12)(PORT=23730))
WARNING: inbound connection timed out (ORA-3136)
有三种因素会导致这个警告出现：
1.Server gets a connection request from a malicious client which is not supposed to connect to the database , in which case the error thrown is the correct behavior. You can get the client address for which the error was thrown via sqlnet log file.
2.The server receives a valid client connection request but the client takes a long time to authenticate more than the default 60 seconds.
3.The DB server is heavily loaded due to which it cannot finish the client logon within the timeout specified。
第1种可以通过sqlnet.log($ORACLE_HOME/network/log/下)文件确定，第3种可以用top -c查看DB Server的load来确定。
下面再现第2种可能：
通过oracle 11gr2 client 连接db，然后故意输入错误的账号密码，等待60秒钟，检查alert日志文件就可以看到这种warning了。
C:\Users\mdu>sqlplus [email protected]
SQL*Plus: Release 11.2.0.1.0 Production on 星期六 1月 19 13:58:11 2013
Copyright (c) 1982, 2010, Oracle. All rights reserved.
输入口令:
连接到:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning, Real Application Clusters, Automatic Storage Management,
Data Mining and Real Application Testing options
SQL> conn [email protected] ###输入错误的用户名及密码
输入口令:
ERROR:
ORA-01017: invalid username/password; logon denied
警告: 您不再连接到 ORACLE。
SQL> ####此session等待60秒钟不再做任何操作
[email protected]$ tail -20 alert_CHNPELT1.log
***********************************************************************
Fatal NI connect error 12170.
VERSION INFORMATION:
TNS for Linux: Version 11.2.0.2.0 - Production
Oracle Bequeath NT Protocol Adapter for Linux: Version 11.2.0.2.0 - Production
TCP/IP NT Protocol Adapter for Linux: Version 11.2.0.2.0 - Production
Time: 19-JAN-2013 13:59:41
Tracing not turned on.
Tns error struct:
ns main err code: 12535
TNS-12535: TNS:operation timed out
ns secondary err code: 12606
nt main err code: 0
nt secondary err code: 0
nt OS err code: 0
Client address: (ADDRESS=(PROTOCOL=tcp)(HOST=10.64.108.62)(PORT=60809))
WARNING: inbound connection timed out (ORA-3136)
我们发现，已经再现成功了。
为什么要等待60秒钟呢？
因为在sqlnet.ora文件中有一个默认的参数SQLNET.INBOUND_CONNECT_TIMEOUT来控制这个时间，如果没有显式的指定此参数，那么默认就是60秒钟。
如果不想在alert日志中收到这样的报错，可以设置SQLNET.INBOUND_CONNECT_TIMEOUT=0.
下面是从网上搜索的关于SQLNET.INBOUND_CONNECT_TIMEOUT的介绍：
Question: What is the "sqlnet.inbound_connect_timeout" parameter and how do I use sqlnet.inbound_connect_timeout for logging off idle sessions?
Answer: The sqlnet.inbound_connect_timeout parameter is used to limit the time, set in seconds, for a client to connect with the database server and provide the required authentication information.