title: ThreadLocal when using hibernate session/JDO persistenceManager
body: <p>I trying to understand the best prastice of using ThreadLocal for the above questions. From my understanding the reason of using this is to ensure only one session/pm created for entire application. My question is</p>
  
  <ol>
  <li><p>is there any impact of using threadlocal like this on clustering application? (example google app engine) ?</p></li>
  <li><p>if u use "transactional" begin,commit on my application, i do not need to use threadlocal right? since "transaction" already ensure my session open and close properly?  </p></li>
  <li><p>if i need to use "transactional", tx, it should be in threadlocal as well?</p></li>
  <li><p>why not just use "static" instead of "threadlocal" ?</p></li>
  </ol>
  
  <p>i interested to hear feedback from you all regarding advantages/disadvantages of using this techinque?</p>