Detecting Orphan SQLnet Shadow Processes

Given a large Database Server with many Shadow Tasks (100+) attaching from PC clients, how do you identify and kill idle processes associated with rebooted/down PC's?

A user could lock a number of important files then shutdown his system. The shadow task would not go away but when asked the user would not think he was still accessing the system.

Certainly this problem could be tracked down via the lock monitors but that seems very manual and timeconsuming for a large shop.

How do people routinely avoid/clean up this type of problem?

Additionally, we find this senario is a problem when shutting down the system. ie) Are the remaining processes orphan shadow tasks or just users who have not gotten the word to log off?

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Regards, 

Lee E. Parsons                  		
Systems Oracle DBA	 			lparsons_at_world.std.com