IIS random(?) application shutdown

I trap the Application close event in Global.asax, and it reports that it keeps being closed with
ApplicationShutdownReason.HostingEnvironment (which I understand to be normal "idle" practice) or BinDirChangeOrDirectoryRename
Needless to say, I don't change the bin directory.
Both of these happen whens sessions are active and so the application and session variables are reset, with the effect that active users crash.

This happens randomly 10 times a day or more

Do you have any idea why this is happening, or can you suggest how I might diagnose the problem?

 have looked at the machine Application and Windows event logs but I can't see anything happening at the same timeI
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I'd be looking at the size and configuration of the "application pool"

You didn't mention which version of IIS you're using so I can't give you an exact link to look at.  However, you should be able to google it with something like this:

"IIS 7 application pool"
PhotoCompManagerAuthor Commented:
I've checked the app pool - it is unlimited and there's > 1GB of main memory available
OK, then check the event logs for things related to IIS and the App Pool (I'm still thinking it's related to the App Pool)

Whenever you post changes to your web site and the contents of the bin directory change, you'll get that shutdown (and restart) event.

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PhotoCompManagerAuthor Commented:
Now working with Micorsoft support on this
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