title: Cache Isolation Level Warning on Parent Entity
body: <p>After adding a second persistence unit and changing my application's data sources to XADataSource (MySQL), I'm now getting a confusing warning in the glassfish log about isolation levels on my parent entity:</p>
  
  <pre><code>WARN  o.e.p.s.f.j.ejb_or_metadata : Parent Entity BaseEntity has an isolation
  level of: PROTECTED which is more protective then the subclass Contact with
  isolation: null so the subclass has been set to the isolation level PROTECTED.
  </code></pre>
  
  <p>After some research, I think that this isolation level warning message is coming from EclipseLink's caching mechanism.  But I am not specifying an isolation level anywhere in my app, so it appears that something in my configuration has triggered the BaseEntity class to have an isolation level of 'PROTECTED'.  The documentation is silent on what might cause it to be automatically assigned to that level -- see <a href="http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Caching/Shared_and_Isolated" rel="nofollow">user guide</a>.</p>
  
  <p>Minor testing with a single user has shown that the application seems to work as expected, but this warning message doesn't make me feel comfortable rolling it out to the masses.</p>
  
  <p>Can anyone shed some light into this message?  Are my concerns valid?</p>