Information
By setting sites to run under unique Application Pools, resource-intensive applications can be assigned to their own application pools which could improve server and application performance. In addition, it can help maintain application availability: if an application in one pool fails, applications in other pools are not affected. Last, isolating applications helps mitigate the potential risk of one application being allowed access to the resources of another application.
Solution
Open IIS Manager Open the Sites node underneath the machine node Select the Site to be changed In the Actions pane, select Basic Settings Click the Select... box next to the Application Pool text box Select the desired Application Pool Once selected, click OK