With a multiple domain installation, the LDAP directory is organized into distinct, non-intersecting sections, each of which represents a domain found in the Domain Name System (DNS). User, group and resource unique IDs are unique within each domain. For example, there can be only one user in each domain with the uid of jdoe. A distinguished name (DN) is a fully qualified domain name.
Calendar Server supports both of these LDAP directory schema versions: Schema version 1 and Schema version 2. When you run the Directory Server Setup script (comm_dssetup.pl), you can choose either LDAP Schema version 1 or LDAP Schema version 2. Use Schema version 2, unless you have specific reasons for using Schema version 1
The following are two reasons to use Schema version 1:
You already have Schema version 1 and you are not planning on using Delegated Administrator for populating LDAP.
You already have Schema version 1 and you are not planning to use Access Manager features.