【现象】

***********************************************************************Fatal NI connect error 12170.VERSION INFORMATION:TNS for Linux: Version 12.1.0.2.0 - ProductionOracle Bequeath NT Protocol Adapter for Linux: Version 12.1.0.2.0 - ProductionTCP/IP NT Protocol Adapter for Linux: Version 12.1.0.2.0 - ProductionTime: 21-MAR-2018 14:01:26Tracing not turned on.Tns error struct:ns main err code: 12535TNS-12535: TNS:operation timed outns secondary err code: 12606nt main err code: 0nt secondary err code: 0nt OS err code: 0Client address: (ADDRESS=(PROTOCOL=tcp)(HOST=192.168.1.81)(PORT=52933))
Wed Mar 21 14:01:26 2018
WARNING: inbound connection timed out (ORA-3136)
Wed Mar 21 14:01:26 2018***********************************************************************

【原因】

1.DoS***，大量恶意连接，此时报错并终止客户端连接是正确的。

2.正常连接，但是未在SQLNET.INBOUND_CONNECT_TIMEOUT值=60秒内完成登陆验证。

3.数据库服务器负载高，类似HANG住。

【解决方法】

（1）查看当前sqlnet.ora

[oraprod@erpdb PROD_erpdb]$ cat sqlnet.ora
###############################################################
#
# Do not edit settings in this file manually. They are managed
# automatically and will be overwritten when AutoConfig runs.
# For more information about AutoConfig, refer to the Oracle
# E-Business Suite Setup Guide.
#
#$Header: NetServiceHandler.java 120.28.12020000.8 2016/03/30 11:22:32 kmandal ship $
#
###############################################################NAMES.DIRECTORY_PATH=(TNSNAMES, ONAMES, HOSTNAME)
SQLNET.EXPIRE_TIME= 10
SQLNET.INBOUND_CONNECT_TIMEOUT =60
SQLNET.ALLOWED_LOGON_VERSION_SERVER=8

（2）查看当前listener的INBOUND_CONNECT_TIMEOUT_PROD：

LSNRCTL> show inbound_connect_timeout
Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
LISTENER parameter "inbound_connect_timeout" set to 60
The command completed successfully

（3）Oracle建议是sqlnet.ora INBOUND_CONNECT_TIMEOUT的值大于listener.ora--中的INBOUND_CONNECT_TIMEOUT_PROD的值。

例如：

sqlnet.ora
SQLNET.INBOUND_CONNECT_TIMEOUT = 120

listener.ora
INBOUND_CONNECT_TIMEOUT_PROD = 119

验证：

LSNRCTL>show inbound_connect_timeout