title: What can cause an intermitent ORA-12560: TNS:protocol adapter error?
body: <p>I have a poorly written legacy .NET application that is in constant contact with the database throwing up a "No Connection" screen if it detects that connectivity has been dropped.</p>
  
  <p>All machines running this program are configured identically but on two of them we just recently started running into a problem where the No Connection screen comes up regardless of whether there is connectivity or not and won't detect the connection until the computer itself is restarted.</p>
  
  <p>Looking into error logs it seems that the culprit is </p>
  
  <pre><code>ORA-12560: TNS:protocol adapter error
  </code></pre>
  
  <p>But what can possibly be causing this?  Especially since this wasn't happening until just a few weeks ago.</p>