Creating Application Pools

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Applies To: Windows Server 2003, Windows Server 2003 with SP1

When you run IIS 6.0 in worker process isolation mode, you can isolate different Web applications or Web sites in pools, which are called application pools. An application pool is a group of URLs that are routed to one or more worker processes that share the same configuration. The URLs that you assign to an application pool can be for an application, a Web site, a Web directory, or a virtual directory.

In an application pool, process boundaries separate each worker process from other worker processes so that when an application is routed to one application pool, applications in other application pools do not affect that application.

By using an application pool, you can assign specific configuration settings to a worker process (or, in the case of a Web garden, to a set of worker processes) that services a group of applications. For example, you can configure worker process recycling, which offers several configuration options to match the needs of each application. If, for example, you suspect that an application has a memory leak, you might configure the application pools worker process to recycle when its memory use reaches a certain threshold. If another application fails because of the volume of requests that it receives, you can set the application pools worker process to recycle when the application exceeds a specified number of requests.

By creating new application pools and assigning Web sites and applications to them, you can make your server more efficient, reliable, and secure, and ensure that your applications remain available even when a worker process serving an application pool is recycled because of a faulty application.

For more information about the application pool architecture in IIS 6.0, including how application pools work, see IIS 6.0 Architecture. For more information about creating application pools and configuring worker processes, see Configuring Application Pools in IIS 6.0 and Configuring Application Pool Identity with IIS 6.0.