It is important to backup your calendar database. In the world of SQL Databases, special procedures are required for backup. It does not necessarily follow that because your database is on the server it is backed up. Talk to your database administrator and be certain that your calendar database has been added to the backup plan.
The tools to back up the database vary from database to database. It is impossible for us to write any instructions other than:
Back up your data!
The cdaily-3.3.6WEB-INF/misc directory contains sample backup scripts for PostgreSQL and Sybase SQL Anywhere on UNIX.