title: Oracle Express: Getting ORA-12154 error when trying to connect using SQL Plus
body: <p>My computer's operating system is Windows 7 64-bit. I just downloaded and install Oracle Express 11g Windows 64-bit. During installation it ask me to set password for both the SYS and the SYSTEM database accounts which I provide as <strong>P@ssword1</strong>. Everything went ok during installation.   </p>
  
  <p>Now I want to connect using SQL Plus. So I click on <em>All Programs --> Oracle Database 11g Express Edition --> Run SQL Command Line</em> to open SQL Plus. </p>
  
  <p>There I type in <code>connect system/P@ssword1</code> and press Enter key. But I get this error message: <strong>ORA-12154: TNS:could not resolve the connect identifier specified</strong></p>
  
  <blockquote>
    <p>SQL*Plus: Release 11.2.0.2.0 Production on Wed Jan 18 22:19:11 2017</p>
    
    <p>Copyright (c) 1982, 2014, Oracle.  All rights reserved.</p>
    
    <p>SQL> connect system/P@ssword1 <br>ERROR: <br>ORA-12154: TNS:could not resolve
    the connect identifier specified</p>
    
    <p>SQL></p>
  </blockquote>
  
  <p>Why I cannot connect? </p>
  
  <p>Thanks</p>