*********************************************************************** Fatal NI connect error 12170. VERSION INFORMATION: TNS for Linux: Version 12.1.0.2.0 - Production Oracle Bequeath NT Protocol Adapter for Linux: Version 12.1.0.2.0 - Production TCP/IP NT Protocol Adapter for Linux: Version 12.1.0.2.0 - Production Time: 21-MAR-2018 14:01:26 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=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攻击，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
原文地址：http://blog.51cto.com/peenboo/2089915
