Welcome to the 15th installment of Learn Active Directory Design and Administration in 15 Minutes a Week, a weekly series aimed at current IT professionals preparing to write the new Windows Active Directory Design and Administration exams (70-219 and 70-217 respectively), as well as newcomers to the field who are trying to get a solid [...]

I) Forest-Wide Operations Master Roles
Every Active Directory forest must have the following roles:
¦ Schema master
¦ Domain naming master
These roles must be unique in the forest. This means that throughout the entire forest, there can be only one schema master and one domain naming master.
1) Schema Master Role
The domain controller assigned the schema master role controls [...]

There are certain Flexible Single Masters of Operation (FSMO) roles that are Forest Wide Operations Master Roles. This means that no matter how many domains exist in the forest, you will only have one of the those particular FSMO servers in the forest.
The Schema Master Domain Controller handles all of the updates and modifications to [...]

One of the common replies and misunderstood rumors is that the Infrastructure Master (IM) is only allowed to run on a Global Catalog Server (GC) if every Domain Controller (DC) in the Forest is Global Catalog Server. That rumor is just based on misleading wording.
The infrastructure masters job is to compare objects of the local [...]

The Infrastructure Master (IM) is a domain-wide FSMO (Flexible Single Master of Operations) role responsible for an unattended process that “fixes-up” stale references, known as phantoms, within the Active Directory database or DIT (Directory Information Table). Phantoms are created on Domain Controllers (DCs) that require a database cross-reference between an object within their own database [...]

The PDC emulator is one of the five operations master roles in Active Directory. It is used in a domain containing non-Active Directory computers.
It processes the password changes from both users and computers, replicates those updates to backup domain controllers, and runs the Domain Master browser.
When a domain user requests a domain controller for authentication, [...]

The RID Master is one of the operations master roles that exist in each domain in a forest. It controls the sequence number for the domain controllers within a domain.
It provides a unique sequence of RIDs to each domain controller in a domain. When a domain controller creates a new object, the object is assigned [...]