ODP.NET で Oracle に接続するとセッションが残る

http://otn.oracle.co.jp/forum/thread.jspa?threadID=28002579&tstart=-2
http://www.atmarkit.co.jp/bbs/phpBB/viewtopic.php?topic=31392&forum=7
http://otndnld.oracle.co.jp/document/products/oracle10g/102/doc_cd/win.102/B31247-01/toc.htm
http://otndnld.oracle.co.jp/document/products/oracle10g/102/doc_cd/win.102/B31247-01/featConnecting.htm#sthref99