title: Unable to connect with SQLPlus, but it works with SQL Developer
body: <p>Windows 7, Oracle 11.2.0.1; it used to be working fine, not sure what happened lately.  But I am not able to connect to SQL plus using sqlplus, and entering user name and password.</p>
  
  <p>SQL Developer is working fine.  Also the following command is working fine:  </p>
  
  <pre><code>sqlplus system/system@//localhost:1521/ORACUSTOM
  </code></pre>
  
  <p>Though the above command is working fine, some of the scripts are not working (as these scripts try to connect to a different database. So I need to make the following work:</p>
  
  <pre><code>$ sqlplus
  
  SQL*Plus: Release 11.2.0.1.0 Production on Sat Nov 10 19:35:34 2012
  
  Copyright (c) 1982, 2010, Oracle.  All rights reserved.
  
  Enter user-name: system
  Enter password:
  ERROR:
  ORA-12560: TNS:protocol adapter error
  
  Enter user-name:
  </code></pre>
  
  <p>I'd appreciate if you can explain why one approach is working and the other is not.  </p>