This paper describes the mutual consistency maintenance mechanism used in a prototype Data Traffic Management System (DTMS), which was designed and implemented to integrate several independent and stand-alone data systems owned by the U. S. Army, Corp of Engineers (CE). The major design constraints were that no modification to the data systems involved were allowed and that the update to each duplicate copy was to be handled as automatically as possible and in a manner approved by the manager of the system containing the copy. The capabilities of the prototype DTMS and the Mutual Consistency Maintenance Subsystem are discussed. The linkage directory used to support mutual consistency maintenance and the mutual consistency maintenance mechanism are described.