The Database subsystem uses the Berkeley DB from Sleepycat Software (the database API is not public). The Database subsystem stores and retrieves calendar data to and from the database, including events, todos (tasks), and alarms. Calendar data is based on iCalendar format, and the schema used for Calendar Server data is a super set of the iCalendar standard.
For a distributed calendar database, Calendar Server uses the Distributed Wire Protocol (DWP) to provide a networking capability. For more information, see Distributed Database Service: csdwpd.
For information about the calendar database, refer to Chapter 16, Administering Calendar Server Databases with csdb.