Application Pools for IIS

An application pool is a container that server allocates memory to a dynamic Web site, and multiple dynamic sites can exist in the same application pool. If there are too many dynamic sites, which can cause memory-level overflow vulnerabilities that affect all dynamic Web sites on that application pool, if the program pool does not limit its use of memory, it will have an impact on sites that use other program pools, because the server has a certain size of memory. A program pool eats too much memory, relative to other program pool can eat memory will be reduced, resulting in web site access to the phenomenon of lag.

You can recycle the memory of the program pool by tapping recycle manually.

Application Pools for IIS