When we create a new web application in SharePoint using central administration, we get a section of “Reset Internet Information Services“ and by default its set to “Restart IIS Manually”. Many times we keep this option by default and create the application but even after successful web application creation we don’t reset IIS and go further for Site Collection creation without any problem. So what is the use of that option even we don’t do anything manually. So here is the explanation.
Single Server Scenario
When we create a new web application it asks for the Application Pool information to us. We can use an Application pool for new web application from the existing application pools or we can create a new application pool for the web application. Now if we create a new application pool then we need not to reset IIS as the purpose of IIS reset is just to recycle the application pool in which our newly created web application will reside. But if we use the existing application pool then it’s the best and recommended practice to reset IIS as may be of existing application pool will not recognize the new web application some time so we need to recycle this using an IIS reset.
So for the best practices, always go for default option and do an “IISRESET /noforce” manually on application server whenever a new application created in a Single server scenario.
Another option i.e. “Restart IIS Automatically” never applies to application server (In which the CA exists) but this option is used to reset the IIS on other web front end servers reside in Farm. For the Application server either it is single server configuration or farm configuration you must reset IIS manually as it won’t reset IIS automatically for application server.
In the Farm scenario, If “Restart IIS Automatically” option is not selected and you have more than one server in the farm, you must wait until the IIS web site is created on all servers, and then run “IISRESET /noforce” on each Web server. The new IIS site will not be usable until that is completed.
So for the best practices, always select “Restart IIS Automatically” option and do an “IISRESET /noforce” manually on application server whenever a new application created in a FARM scenario.