title: LAST_CONVERT column in DBA_LOCK
body: <p>What is the significance of LAST_CONVERT column in <a href="http://docs.oracle.com/cd/E11882_01/server.112/e25513/statviews_4111.htm#REFRN23116" rel="nofollow">DBA_LOCK</a>? There doesn't appear to be anything relevant in the documentation and I could not find anything elsewhere. What is the idea behind this column? </p>
  
  <p>Also, is a good way to find out for how long a lock is being held?</p>