title: Can't Connect to SQL*Plus using SID
body: <p>I executed the following query to find the SID of the database that I was connected to as system:</p>
  
  <pre><code>SQL&gt; select sys_context('userenv','instance_name') from dual;
  
  SYS_CONTEXT('USERENV','INSTANCE_NAME')
  --------------------------------------------------------------
  orcl
  </code></pre>
  
  <p>I then try connecting to system with the following command:</p>
  
  <pre><code>C:\&gt;sqlplus system/system@orcl
  
  SQL*Plus: Release 12.2.0.1.0 Production on Wed Aug 8 23:53:02 2018
  
  Copyright (c) 1982, 2016, Oracle.  All rights reserved.
  
  ERROR:
  ORA-12154: TNS:could not resolve the connect identifier specified
  </code></pre>
  
  <p>What can I do to connect to the database as system while specifying the SID? </p>