In IIS7 for Windows 2008, you can set up application pools so you can isolate different websites, for example, so that they’re all not using the same instance. It is a grouping of URLs that is routed to one or more worker processes. Application pools define a set of web applications that share one or more worker processes, they provide a convenient way to administer a set of Web sites and applications and their corresponding worker processes. Process boundaries separate each worker process; therefore, a website or application in one application pool will not be affected by application problems in other application pools. Application pools significantly increase both the reliability and manageability of a web infrastructure.
If you are running 3 websites on your IIS server and you have them in separate application pools, you can restart one that’s having an issue without impacting the other two sites.
1. To restart IIS for a specific application pool, start IIS Manager
2. Expand the Application Pools menu
3. Click on the app pool you’d like and choose “Recycle”