In this chapter, we covered how objects are grouped at a high level into naming contexts and application partitions, which are used as replication boundaries. The Domain NC contains domain-specific data such as users, groups, and computers. The Configuration NC contains forest-wide configuration data such as the site topology objects and objects that represent naming contexts and application partitions. The Schema NC contains all the schema objects that define how data is structured and represented in Active Directory. Application partitions were introduced in Windows Server 2003 Active Directory as a way for administrators to define their own grouping of objects and, subsequently, replication boundaries. Storage of DNS data for AD-Integrated DNS zones is the classic example of when it makes sense to use application partitions, due to the increased control they give you over which domain controllers replicate the data. Dynamic objects are also new to Windows Server 2003 Active Directory; they allow you to create objects that have a time-to-live (TTL) value. After the TTL expires, Active Directory automatically deletes the object.