 <p>Solved similar case a few times. It's very difficult (I call it lucky) to find solution in complicated app just from your session logging. (Oracle kills one of these sessions. One is killed and the other one lives on happily)</p> <p>Best solution is to ask your DBA (or if you have access to your oracle instalation, you can google and then get them yourself, it's not sou complicated) for trace file(this file is mentioned in exception of killed session, so search your alert log), there will be deadlock graph. (just fulltext trace file for DEADLOCK)</p> <p>Just look here for exact information how to look into your trace file. <a href="http://www.oracle-base.com/articles/misc/deadlocks.php" rel="nofollow">LINK</a></p>