The steps in this section, and in Preparing to migrate existing users and groups and Migrating existing users to hierarchical zones, are iterative in nature. In most cases, you will select a subset of computers for deployment, and repeat the steps for each target group until you have migrated all of the computers and users in the enterprise into Active Directory.
There is no technical requirement that you only work with a subset of computers at a time, but in practice the process of checking computers for potential problems and resolving open issues is more manageable when applied to a subset of computers. It is also more practical to migrate user populations in stages rather than all at once. After you step through the process a few times, you’ll be able to anticipate and resolve potential issues more quickly and move into a more rapid deployment model.