11gR2: Listener hangs with ORA-12518 and too many open files

How up to date are you on bugs fixed in 11.2.0.4 which affect 11.2.0.1, 11.2.0.2 and 11.2.0.3?  Were you aware there is an unpublished bug related to this and also a patch for 11.2.02 and 11.2.0.3 which can resolve this for you?  Read "11.2 : ORA-12518 Listener Hangs and Reports "Too Many Open Files" on My Oracle Support from document ID 1527483.1 and also see how you can monitor open sessions with lsof which is something featured in this article where we had problems with open connections ourselves.