A common problem when migrating objects from one forest to another using Microsoft’s ADMT (Active Directory Migration Tool) is the inability of the tool to migrate SID history for windows standard domain global groups such as "Domain User" or "Domain Admins." Typically what happens is in situations where administrators have used these groups to assign permissions such as in file and directories on a file and print server, users no longer have access to these files and directories during the interoperability stage of a migration. This stage is when users, groups and workstations have all been migrated to the new forest, but the application servers still remain in the source domain.