Active Directory Schema

Every single object and attribute that is present within an Active Directory is generally defined in a schema, which is nothing but an Active Directory component. Now, as Active Directory stores information from diverse services and applications, all that information is primarily standardized with the help of a schema. The Active Directory schema actually helps in defining how the data is stored and how the directory service will recover, revise or reproduce the data while ensuring that the integrity of data remains intact.

In Active Directory, it won't be wrong to consider Objects as the key storage units. In fact, they are defined under the AD schema. Every time some information is to be handled, the directory queries the schema for appropriate definition of object. The AD creates the objects and stores data in it as per the definition available in the schema, because the schema has got the ability of controlling the type of information that can be stored in the objects. Data types which usually present in schema definitions can also be stored in the objects. However, in situations where one has to store a new data type, a new object definition needs to be created in the schema.

The object definition in the AD schema includes all the object attributes together with the definitions of the attribute relationships. To make it more clear just for an example, a User object will enclose an attribute user's logon name. This attribute will sequentially hold other attributes like syntax of the logon name. Therefore, every single object attribute and the attribute within are defined in the schema of the Active Directory.

Building Active Directory Schema

During the creation of forest at the time of Active Directory installation, the default schema too gets created. The default schema is generally gets replicated in every new domain thereafter created within the forest and as a result each Domain Controller gets permission to access to a copy of the default schema. This is necessary for creating objects within the domain as it is quite essential that the DC have the object definitions because it is play a very important role in creating objects and storing or retrieving information in the Active Directory. The replication topology of Active Directory ensures that every domain controller will be competent enough to write changes in the AD database and after that replicate those changes to other DCs in the same forest.

Active Directory Schema architecture

Schema is the Active Directory component and it defines almost all the AD objects along with their attributes. The physical structure of Active Directory schema comprises of definitions of object. In general the schema is stored in the schema partition of the directory and further defines the following:

• Objects used to store data in the directory
• Rules that govern the structure of the objects
• Structure of directory and its content

The above definitions consist of objects, attributes and classes, the details of which are mentioned below:

Schema components

1. Objects
2. Attributes
3. Classes
4. Schema objects