You must run the utility locally on the machine where Calendar Server is installed.
If you are restoring the calendar database, Calendar Server must be stopped.
You must be logged in as the user and group under which Calendar Server is running (such as icsuser and icsgroup) that was specified during installation, or as root.
csrestore does not take care about the user LDAP entries, subscribed or own calendar. You need to manually perform on the User LDAP entire to get the personal calendar back on the multi valued attribute, icsSubscribed.