title: Oracle: why parallel delete doesn't go parallel?
body: <p>I've tried the following statement. But it doesn't proceed parallel. Why?
  How can I speed up the operation?</p>
  
  <pre><code>ALTER SESSION ENABLE PARALLEL DML;
  
  DELETE /*+ parallel(20) */
        FROM  table
        WHERE flag != 'N';
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/6AymU.png" alt="enter image description here"></p>