Instalación y actualización > Installation and Configuration Guide > Database Installation > Installing SQL Server > Installation Steps > Set Up Windows Service Accounts for the Database
  
Set Up Windows Service Accounts for the Database
SQL Server requires Windows-based service accounts for the underlying services that power the database server. These can be domain- or server-based depending on the type of SQL Server installation. These accounts should not be domain administrators, nor is it a requirement to make them administrators on the server that will host SQL Server. For additional information see:
Setting Up Windows Service Accounts
http://msdn.microsoft.com/en-us/library/ms143504.aspx
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These accounts are separate from the logins and users used by Windchill.