SharePoint 2010 Application Pool

There might be a situation where you want to alter the identity for the IIS application pool under which your SharePoint 2010 web applications are running.

You might be tempted to navigate to the IIS settings and alter the identity in there:

This is not recommended.
It’s best practice to run application pools under a domain user account, i.e. SP_ServiceApps. This account is best managed using Managed Accounts.
To change the identity for an application pool, log into Central Administration and follow these steps:

1. Go to Security and under General Security, click Configure Service Accounts.
2. Select the application pool from the components drop-down listbox (1)
3. Select the managed account (2) that you want to use as
   the identity for this application pool, or register a new managed
   account in SharePoint 2010, using the Register a new managed account link.
4. Click the OK button.
5. You’ll be warned that this action requires an IIS reset on all servers, click OK.
6. Perform a iisreset /noforce on all WFE servers in the farm.