LDAP Schema 1 is a provisioning schema that consists of both an Organization Tree and a DC Tree. This set of schema (at the time, it was simply called “schema”) was supported in previous Calendar Server 5.x versions.
When Calendar Server searches for user or group entries, it looks at the user's or group’s domain node in the DC Tree and extracts the value of the inetDomainBaseDN attribute. This attribute holds a DN reference to the organization subtree containing the actual user or group entry.
Only sites that have installed previous versions of Calendar Server should use Schema 1.
Migrating to Schema 2 is imperative if you plan to install Calendar Server with other Sun Java System products in the future.
Schema 1 supports LDAP provisioning tools. For more information, see Understanding Provisioning Tools.