Idle Time-out Settings for an Application Pool

can someone explain for me this sentence from msdn ?

Idle time-out can be helpful in the following situations: The s开发者_C百科erver has a heavy processing load.

is the idle timeout for the w3wp.exe process or each user that's connected to the website has a nested process inside the w3wp and this is the idle time for this nested process? if it's the idle process for w3wp as a whole , then what does msdn sentence mean??

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It prevents a application pool worker process from hanging around when no users are hitting the web pages hosted by the worker process. When the users stop hitting the web site for a while, IIS stops the process.

This can be annoying if you have an expensive setup/teardown process for the application, such as populating a cache.

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The idle timeout is per application pool. You can observe the running pools as well as in IIS in VS by Tools > Attach to Process then I click the Process column header to bring any running w3wp.exe's to the top.

You can set the timeout for each app pool in IIS7+ in Advanced Settings... Process Model section.