title: GATHER_PLAN_STATISTICS does does not generate basic plan statistics
body: <p>all,</p>
  
  <p>I am learning to tune query now, when I ran the following:</p>
  
  <pre><code>select /*+ gather_plan_statistics */ * from emp;
  
  select * from table(dbms_xplan.display(FORMAT=&gt;'ALLSTATS LAST'));
  </code></pre>
  
  <p>The result always says:</p>
  
  <blockquote>
    <ul>
    <li>Warning: basic plan statistics not available. These are only collected when:
    
    <ul>
    <li>hint 'gather_plan_statistics' is used for the statement or</li>
    <li>parameter 'statistics_level' is set to 'ALL', at session or system level</li>
    </ul></li>
    </ul>
  </blockquote>
  
  <p>I tried the <code>alter session set statistics_level = ALL;</code> too in sqlplus, but that did not change anything in the result.</p>
  
  <p>Could anyone please let me know what I might have missed?</p>
  
  <p>Thanks so much.</p>