oracle 环境变量 could not resolve the connect identifi

初学oracle,    在电脑上安装了Oracle 10g 后用sqlplus登录一切正常 . 但当安装完Oracle 10g client后,问题出现了,用sqlplus登录时反复提示:could not resolve the connect identifier specified， 但用客户端工具如sqldeveloper连进去，一点问题都没有！

然后查了ORACLE的文档， 说明如下：

Cause: A connection to a database or other service was requested using a connect identifier, and the connect identifier specified could not be resolved into a connect descriptor using one of the naming methods configured. For example, if the type of connect identifier used was a net service name then the net service name could not be found in a naming method repository, or the repository could not be located or reached.
Action:

- If you are using local naming (TNSNAMES.ORA file):

- Make sure that "TNSNAMES" is listed as one of the values of the NAMES.DIRECTORY_PATH parameter in the Oracle Net profile (SQLNET.ORA)

- Verify that a TNSNAMES.ORA file exists and is in the proper directory and is accessible.

- Check that the net service name used as the connect identifier exists in the TNSNAMES.ORA file.

- Make sure there are no syntax errors anywhere in the TNSNAMES.ORA file. Look for unmatched parentheses or stray characters. Errors in a TNSNAMES.ORA file may make it unusable.

- If you are using directory naming:

- Verify that "LDAP" is listed as one of the values of the NAMES.DIRETORY_PATH parameter in the Oracle Net profile (SQLNET.ORA).

- Verify that the LDAP directory server is up and that it is accessible.

- Verify that the net service name or database name used as the connect identifier is configured in the directory.

- Verify that the default context being used is correct by specifying a fully qualified net service name or a full LDAP DN as the connect identifier

- If you are using easy connect naming:

- Verify that "EZCONNECT" is listed as one of the values of the NAMES.DIRETORY_PATH parameter in the Oracle Net profile (SQLNET.ORA).

- Make sure the host, port and service name specified are correct.

- Try enclosing the connect identifier in quote marks. See the Oracle Net Services Administrators Guide or the Oracle operating system specific guide for more information on naming.

所以根据文档我反复检查TNSNAMES.ORA 文件的内容及配置Net Manager，怎么弄问题还是一样。  

突然想到环境变量的问题，果然发现我当前的环境变量设置的不对， 可能是因为安装oracle client 引起的。

当我们用比如sqldeveloper连数据库时 它不依赖于系统的环境变量， 所以没问题

啊 ！ 苦难终于度过了， 见光明。。。。。 Thanks Godness!

继续以后的学习