Performance monitor shows 4294967293 sessions active

Question

I have an ASP.Net 3.5 website running in IIS 6 on Windows Server 2003 R2. It is a relatively small internal application that probably serves less than ten users at any given time. The server has 4 Gig of memory and shows that 3+ Gig is available while the site is active.

Just minutes after restarting the web application Performance monitor shows that there is a whopping 4,294,967,293 sessions active! I am fairly certain that this number is incorrect; at the time this reading there were only 100 requests to the website.

Has anyone else experienced this kind odd behavior from perf mon? Any ideas on how to get an accurate reading?

UPDATE: After running for about an hour the number of active sessions has dropped by 4. So it does seem to be responding to sessions timing out.

Answer 1

Well, 2^32 = 4,294,967,296, so sounds like there's some kind of overflow occurring. Can't say exactly why.

Answer 2

Could be an overflow, but my money's on an underflow. I think that the program started with 0 people, someone logged off, and then the number of sessions went negative.

Answer 3

I am also showing a high number, currently 4,294,967,268.

Every time I abandon a Session, the Sessions abandoned count goes up by 1, and the Sessions Active count decreases by 1. Currently my abandoned session count = 16, so this number probably started at 4,294,967,84.

Is there a fix for this?

Answer 4

We have the same problem. It looks like MS has a Hotfix available: http://support.microsoft.com/kb/969722

Update 9/10/2009: Our IT department contacted MS for the Hotfix. It fixed our issue. We are running .NET 2.0 if it matters any.

Answer 5

My counters were working fine, but one morning I logged in remotely to the production server, and the counter was on this huge number (which is as somebody mentioned very close to 2^32 indicating an underflow). But the only difference from the day before when everything worked was the fact that during the night, windows had installed updates. So for some reason these updates caused this pretty annoying error.

Observing the counter a little more, I found out that whenever the application is restarted - after some time with no traffic, the counter starts correctly at zero. When users start logging on, it increments fine. When they start logging off again, it still decrements fine until it reaches what is supposed to be zero. At that point it goes bananas...

Sigh...

Answer 6

If you have to use your existing statistics, I opened the log file in Excel and used a formula to bring a more accurate value. I cannot guarantee its accuracy, but the results did look okay:

If B2 is the (aspnet_wp)\Sessions Active value , and the formula sits in C2

/* This one is quicker as it doesn't have to do the extra calculations */
=IF(B2>1073741824,4294967296-B2,B2)

Or

/* This one is clearer what is going on */
=IF(B2>power(2,30),(4*power(2,30))-B2,B2)

P.S. (I feel your pain - I have to explain why they have 4.2 billion sessions opening whereas a second earlier they had 0!)