硬件说明：
操作系统版本：ORACLE LINUX 6.3 64位
数据库版本：11.2.0.3 64位
问题说明：
在检查数据库的alert日志的时候，发现大量的12170和TNS-12535的错误；
Fatal NI connect error 12170.
VERSION INFORMATION:
TNS for Linux: Version 11.2.0.3.0 - Production
Oracle Bequeath NT Protocol Adapter for Linux: Version 11.2.0.3.0 - Production
TCP/IP NT Protocol Adapter for Linux: Version 11.2.0.3.0 - Production
Time: 06-APR-2014 10:46:14
Tracing not turned on.
Tns error struct:
ns main err code: 12535
TNS-12535: TNS:operation timed out
ns secondary err code: 12560
nt main err code: 505
TNS-00505: Operation timed out
nt secondary err code: 110
nt OS err code: 0
Client address: (ADDRESS=(PROTOCOL=tcp)(HOST=110.80.1.83)(PORT=50226))
Sun Apr 06 10:46:24 2014
问题解决：
在metalink平台上面查找，该症状和文档 ID （1628949.1）描述的症状完全一样，根据文档的内容整理如下：
1、出现问题的版本
Oracle Net Services - Version 11.2.0.3 to 12.1.0.1 [Release 11.2 to 12.1]Information in this document applies to any platform.
2、出现错误的症状或报错格式如下：
Fatal NI connect error 12170.VERSION INFORMATION:TNS for 64-bit Windows: Version 11.2.0.3.0 - ProductionOracle Bequeath NT Protocol Adapter for 64-bit Windows: Version 11.2.0.3.0 - ProductionWindows NT TCP/IP NT Protocol Adapter for 64-bit Windows: Version 11.2.0.3.0 - ProductionTime: 22-FEB-2014 12:45:09Tracing not turned on.Tns error struct:ns main err code: 12535TNS-12535: TNS:operation timed outns secondary err code: 12560nt main err code: 505TNS-00505: Operation timed outnt secondary err code: 60nt OS err code: 0***Client address: (ADDRESS=(PROTOCOL=tcp)(HOST=121.23.142.141)(PORT=45679))
The PORT field here is the ephemeral port assigned to the client for this connection. This does not correspond to the listener port.
3、问题的原因
The alert.log message indicates that a connection was terminated AFTER it was established to the instance. In this case, it was terminated 2 hours and 3 minutes after the listener handed the connection to the database.
This would indicate an issue with a firewall where a maximum idle time setting is in place.
The connection would not necessarily be "idle". This issue can arise during a long running query or when using JDBC Thin connection pooling. If there is no data 'on the wire' for lengthy
periods of time for any reason, the firewall might terminate the connection.
4、解决方法：
The following parameter, set at the **RDBMS_HOME/network/admin/sqlnet.ora, can resolve this kind of problem. DCD or SQLNET.EXPIRE_TIME can mimic data transmission between the server and the client during long periods of idle time. SQLNET.EXPIRE_TIME=n Where <n> is a non-zero value set in minutes.
进入ORACLE_HOME/network/admin目录下，添加sqlnet.ora文件，增加一行SQLNET.EXPIRE_TIME=10
5、补充说明SQLNET.EXPIRE_TIME
Purpose
To specify a time interval, in minutes, to send a check to verify that client/server connections are active. The following usage notes apply to this parameter:
- Setting a value greater than 0 ensures that connections are not left open indefinitely, due to an abnormal client termination.
- If the probe finds a terminated connection, or a connection that is no longer in use, then it returns an error, causing the server process to exit.
- This parameter is primarily intended for the database server, which typically handles multiple connections at any one time.
- Limitations on using this terminated connection detection feature are:
- It is not allowed on bequeathed connections.
- Though very small, a probe packet generates additional traffic that may downgrade network performance.
- Depending on which operating system is in use, the server may need to perform additional processing to distinguish the connection probing event from other events that occur. This can also result in degraded network performanc
6、做完以上操作后，重启数据库的监听；
详细的metalink链接 ：https://support.oracle.com/epmos/faces/DocumentDisplay?id=1628949.1