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Message Posted: Fri, 14 Sep 2001 @ 14:02:37 GMT

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Subj:   Re: Number of ACTIVE users
From:   John Hall

This is called a 'Phantom Session' where a session appears and yet the user is no longer logged-on. You'll also see the situation where there is spool space, but there is no query running. These have been around since Day 1 (I first saw them back in 1983 when I started at Teradata).

A fix for a Phantom Session is like a cure for the common cold: there's nearly a 100 infections which give the symptoms for a cold and there's no medicine which can cure all of them. By the time you can identify which one you have, it's too late - you're already back to work.

Over the years, I know that Phantom Sessions have been regularly reported, debugged and that various fixes were applied. I imagine if no further improvements with TOS had occurred, then Phantom Sessions would be a thing of the past. Reality is that there have been a lot of significant improvements to the Teradata and so we still see Phantom Sessions. I'm not excusing them, I've just learned how to live with them.

Generally speaking, the Phantom Session is harmless and will go away with the next restart. At the same time, I have seen Phantom Sessions accumulate and eventually start to impact system performance. Again, a restart was all that was necessary to clear them up. Whether you want to schedule a restart is dependent on whether you feel that they are impacting your system (like eating-up a lot of spool) or if they are harmless.

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