What is a schema update?

Applies To: Windows SBS 2008

The schema is the Active Directory Domain Services (AD DS) component that defines all the objects and attributes that the directory service uses to store data.

AD DS stores and retrieves information from a wide variety of applications and services. So that it can store and replicate data from a potentially infinite variety of sources, AD DS standardizes how data is stored in the directory. By standardizing how data is stored, AD DS can retrieve, update, and replicate data, while maintaining the integrity of the data.

The schema for AD DS in Windows SBS 2008 is not the same as the schema for Active Directory in Windows SBS 2003 or in Windows Server 2003. To successfully complete the migration process, you must update the schema on the Source Server if it is running either Windows SBS 2003 or Windows Server 2003.


You should back up your Source Server before you run the Migration Preparation Tool. All changes that the Migration Preparation Tool makes to the schema are irreversible.

Use the Migration Preparation Tool to prepare the Source Server for the migration process. The Migration Preparation Tool performs the following tasks:

  • Runs adprep.exe, which extends the schema and updates permissions as necessary to prepare a forest and domain for a domain controller that runs Windows SBS 2008.

  • Installs an update that extends the time limit for finishing the migration process. Only one server running Windows SBS 2008 or Windows SBS 2003 is allowed to be a domain controller on your network. For a migration, you can have both domain controllers on your network for a limited time period. The update extends this time period to 21 days.

  • Prepares to migrate Exchange Server.

You must be a member of all of the following groups to run the Migration Preparation Tool:

  • Enterprise Admins

  • Schema Admins

  • Domain Admins