Understanding Stopping/Starting vs. Recycling Application Pool

Application Pool Stopping/Starting vs. Recycling

When you stop an application pool, you are instructing all ISS worker processes serving the application pool to shut down. This prevents any additional worker processes from being started until the application pool is started again.  This initiates a graceful shutdown of the worker processes, with each worker process attempting to drain all of it’s requests and then exit.

When you recycle an application pool all currently running IIS worker processes in that application pool are  gracefully shutdown, but unlike stopping the pool, new IIS worker processes can be started on demand to handle subsequent requests.

Recycling an application pool is a good way to cause the reset of application state and any configuration cached by the IIS worker processes that does not get automatically refreshed (mostly global registry keys), without disrupting the operation of the server. This makes recycling the application pool a great alternative to an IISRESET in most cases.