The general concept of Flexible Single Master Operations (FSMO) roles working closely together with Active Directory (AD) using five specific server roles. When it comes to installing Active Directory Domain Services it creates a forest which holds all the FSMO’s roles for each new domain that you add to active directory. FSMO roles have been implemented to perform a job that avoids corruption due to conflicting simultaneous changes; they are performed by one specific server that prevents database corruption. These five specific server roles are divided between domain-wide and forest-wide operations. There are three roles that are domain specific these include, Relative Identifier (RID) Master, Infrastructure Master, and Primary Domain Controller (PDC) Emulator.
The RID has a responsibility of creating a team of identifiers used when new accounts, groups, and computers are created. This is a part of security identifiers (SID) which is used to identify an object throughout the domain. The Infrastructure Master is accountable for replicated changes to an object’s SID or distinguished name (DN). Infrastructure Master and global catalog work closely together but are not serviced on the same domain controller due to the fact that if they were on the same domain controller it would be difficult to know the other information has changed. Last one on the list the Primary Domain Controller Emulator (PDC) is held accountable for managing time synchronization within a domain edits to Group Policy Objects (GPO), and replication of security-sensitive account events, such as password changes and account lockouts.
The forest-wide FSMO roles provide a function which is unique in all domains; they keep track of adding and removing domain names and manage changes to the AD schema. In the AD the forest-wide authorities are Domain Naming Master (DMN) and Schema Master (SM). When creating a new domain the DM assures the name has never been used. Lastly, the SM role takes care of all changes the happen within AD. As an object class or attribute is modified it becomes the SM responsibility to assure the change is replicated throughout all the domains in the forest.
Now that we know the basics of understanding each of the FSMO roles and its function then it will be easier to recover from a failed role and managing all existing roles through role transfer and role seizure. Knowing all the FSMO roles will make it easier for a network administrator to locate and execute the problem as it occurs or even to prevent a problem from occurring.