When you configure resources, you will specify which entries to synchronize based on their objectclass. Object class(es) determine which attributes will be available to synchronize for both Directory Server and Active Directory.
Objectclasses are not applicable for Windows NT
Identity Synchronization for Windows supports two types of objectclasses:
Structural Objectclasses: Every entry that’s created or synchronized from the selected Directory Server must have at least one structural objectclass. Select a structural objectclass from the drop-down list. (Defaults to inetorgperson on Directory Server and User on Active Directory)
Directory Server allows you to select one or more objectclasses from the Available Auxiliary Object Classes list pane to augment the selected structural class, which provides additional attributes for synchronization.
For detailed information about configuring objectclasses and attributes, see Chapter 6, Configuring Core Resources