Each LDAP object class or attribute must be assigned a unique name and object identifier (OID). When you define a schema, you need an OID that is unique to your organization. One OID is enough to meet all of your schema needs. You then add new branches on that OID for your attributes and object classes.
Obtaining and assigning OIDs in your schema involves doing the following:
Obtaining an OID for your organization from the Internet Assigned Numbers Authority (IANA) or a national organization.
In some countries, corporations already have OIDs assigned to them. If your organization does not already have an OID, you can obtain an OID from IANA.
Creating an OID registry so you can track OID assignments.
An OID registry is a list that you maintain, which gives the OIDs and OID descriptions that are used in your directory schema. A OID registry ensures that no OID is ever used for more than one purpose.
Creating branches in the OID tree to accommodate schema elements.
Create at least two branches under the OID branch or your directory schema, using OID.1 for attributes and OID.2 for object classes. If you want to define your own matching rules or controls, you can add new branches as needed, such as OID.3.