In looking through managed-prevalence.lisp, it appears that the "unique" id counter isn't saved in the transaction log. Is this an oversight, or a feature I don't understand? :) The relevant section is copied in below: (defun tx-create-id-counter (system) "Initialize the id counter to 0" (setf (get-root-object system :id-counter) 0)) (defmethod next-id ((system prevalence-system)) "Increment and return the next id" (incf (get-root-object system :id-counter))) -- Randall Randall <randall@randallsquared.com> Property law should use #'EQ , not #'EQUAL .