Are you integrating Calendar Server with other Java Enterprise System component products, such as Portal Server or Access Manager, which provide single sign-on capabilities?
Are you installing Calendar Server for the first time or are you upgrading from an older version?
If you are installing Calendar Server for the first time, use Schema 2 Native Mode.
If you are upgrading from an older version of Calendar Server, you can either use Schema 1 or Schema 2 Native or Compatibility Mode.
If you answer Yes, use Schema 2 Native or Compatibility Mode.
Do you want to use the Calendar Server csdomain utility for provisioning domains?
If you answer Yes, use Schema 2 Native or Compatibility Mode. If you don’t plan to use the csdomain utility, and you have an existing Calendar Server installation, use Schema 1.
If you don’t want to use either Access Manager or Calendar Server CLI utilities for provisioning, use can use either Schema 2 Native Mode for new installations, or Schema 1 or Schema 2 Compatibility Mode for existing Calendar Server installations.