环境：
服务端：RHEL6.5 + Oracle Server 11.2.0.4
客户端：Win2003 + Oracle Client 10.2.0.1
1.问题现象
2.Troubleshooting
3.解决问题
1. 问题现象
服务端安装好Oracle数据库，测试正常。
但在用户的客户端测试连接时，报错ORA-12154，TNS-03505
sqlplus system/oracle@192.168.10.10/xxsid
C:\Documents and Settings\Administrator>sqlplus system/oracle@192.168.10.10/xxsid
SQL*Plus: Release 10.2.0.1.0 - Production on 星期四 7月 16 16:53:58 2015
Copyright (c) 1982, 2005, Oracle. All rights reserved.
ERROR:
ORA-12154: TNS: 无法解析指定的连接标识符
请输入用户名:
2. Troubleshooting
tnsping测试：
C:\Documents and Settings\Administrator>tnsping 192.168.10.10
TNS Ping Utility for 32-bit Windows: Version 10.2.0.1.0 - Production on 16-7月 -
2015 16:53:00
Copyright (c) 1997, 2005, Oracle. All rights reserved.
已使用的参数文件:
D:\oracle32\product\10.2.0\client_1\network\admin\sqlnet.ora
TNS-03505: 无法解析名称
查看已使用的参数文件sqlnet.ora
# sqlnet.ora Network Configuration File: D:\oracle32\product\10.2.0\client_1\network\admin\sqlnet.ora
# Generated by Oracle configuration tools.
# This file is actually generated by netca. But if customers choose to
# install "Software Only", this file wont exist and without the native
# authentication, they will not be able to connect to the database on NT.
SQLNET.AUTHENTICATION_SERVICES= (NTS)
NAMES.DIRECTORY_PATH= (TNSNAMES)
发现NAMES.DIRECTORY_PATH的配置只允许TNSNAMES
3. 解决问题
注释掉sqlnet.ora中NAMES.DIRECTORY_PATH= (TNSNAMES)一行，
注释掉就会采用默认值(TNSNAMES，ONAMES，HOSTNAME)，当然你也可以修改加上这些常用选项。
再次测试，问题解决。
C:\Documents and Settings\Administrator>sqlplus system/oracle@192.168.10.10/xxsid
SQL*Plus: Release 10.2.0.1.0 - Production on 星期四 7月 16 16:54:08 2015
Copyright (c) 1982, 2005, Oracle. All rights reserved.
连接到:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL>
如果没有特殊的安全需求或其他规范，建议还是不要随意更改sqlnet.ora文件的配置信息。