FSMO Roles.

Flexible Single Master Operations Roles :

Forest wide Master Operation: 

1. Schema master 2.Domain Naming master

Domain wide master operation: 
3. PDC emulator
4. RID master
5. Infrastructure master

1.Schema Master: 

Responsible for overall management of the entire schema in a forest.
The first DC installed acts as a schema master in the entire forest.
There can be only one schema master in the entire forest

2.Domain Naming Master: 

Responsible for addition /removal of domains.
It maintains the uniqueness of domain names.
There can be only one DNM in the entire forest.

3. PDC emulator: 

PDC provides backward compatibility for existing NT BDCs and workstations. (If it is running in mixed mode)
PDC updates the password changes made by the users.
It is also responsible for synchronizing the time.
There can be only one PDC emulator per domain.

4. RID master: 

Responsible for assigning unique IDs to the objects created in the domain.
There can be only one RID master per domain
SID – Security Identifier it maintains a access control list. It is divided into two parts.
1. DID (Domain Identifier)
2. RID (Relative Identifier)

For knowing the SID of the user
>Start>run>cmd> whoami /user.

5. Infrastructure master: 

Responsible for maintaining the updates made to the user & group membership.
It also maintains universal group membership.
There can be only one infrastructure master per domain

The term flexibility means we can transfer any of the 5 roles from DC to ADC.