title: GAE transaction exceptions
body: <ol>
  <li>In this example, is the exception being thrown if any of the table elements are being changed by another client, or only if the element that we changed has been changed by another client?</li>
  <li><p>Just to verify - the exception is thrown from the <code>commit()</code> isn't it?</p>
  
  <pre><code>PersistenceManager pm = PMF.get().getPersistenceManager();    
  try {
      pm.currentTransaction().begin();
      List&lt;Row&gt; Table = (List&lt;Row&gt;) pm.newQuery(query).execute();
      Table.get(0).setReserved(true);    // &lt;----- we change only this element
      pm.currentTransaction().commit();
  } catch (JDOCanRetryException ex) {
      pm.currentTransaction().rollback() // &lt;----- if Table.get(1) was changed by another client do we get to this point??? 
  }
  </code></pre></li>
  </ol>