IIS Service Disruption: What all causes them?

Question

I haven't found a definitive list out there, but hopefully someone's got one going or we can come up with one ourselves. What causes disruptions for .NET applications, or general service disruption, running on IIS? For instance, web.config changes will cause a recompilation in JIT (while just deploying a single page doesn't affect the whole app), and iisresets halt everything (natch, but you see where I'm going). How about things like creating a new virtual directory under a current web app?

It's helpful to know all the cases so you know if you can affect a change to a server without causing issues with the whole thing.

EDIT: I had IIS 6 in mind when I asked, but of course a list of anything different in other versions would be helpful as well to people.

Answer 1

See this question: http://stackoverflow.com/questions/302110/what-causes-an-application-pool-in-iis-to-recycle

Answer 2

It depends on what exactly you are talking about with disruptions. IISReset can cause a Service Unavailable message to display for a short time as IIS is shutdown and re-started.

Changes to the web.config, or adding a .dll file to the bin directory of an application causes a recycle of the application domain but that is not a disruption exactly, more of a "delay" in responding, the user will NOT see an error just a delayed response from the server. You can also get that from changing any files in App_Code or .vb files on non WAP developed sites.

You can also get IIS Worker Process Shutdowns due to inactivity, default setting is 20 minutes. Again this is a delay, not a lack of service.