My Lisp is a bit rusty, but I think actual constants are written +with-pluses+, whereas * the-stars * indicate global variables. And that database isn't just internally mutable, sometimes it's replaced completely [0]:

  (defun load-db (filename)
    (with-open-file (in filename)
      (with-standard-io-syntax
        (setf *db* (read in)))))

[0]: http://www.gigamonkeys.com/book/practical-a-simple-database....