developer suite链接到oracle服务器

Developer Suite连接数据库的问题，劳驾高手指点！
电脑里面同时装了OraHome92和DevSuiteHome2，前者的sql*plus能访问，后者的则不行。输入scott/tiger登陆后者时，我输入了"主机字符串"号以后，报错： 
  ORA-12154: TNS:无法解析指定的连接标识符

******在网上找了很长时间都找不到合适的对策，其中有人建议：
  1.打开OC4J listner, 然后在dos命令中输入'lsnrctl start listener'，报错如下：
Copyright (c) 1991, 2002, Oracle Corporation. All rights reserved.

启动tnslsnr：请稍候...

Service OracleOraHome92TNSListener already running.
TNS-12560: TNS: 协议适配器错误
TNS-00530: 协议适配器错误
  32-bit Windows Error: 1056: Unknown error
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2.国外网站上人家的建议  
ORA-12154: TNS:could not resolve the connect identifier specified 
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