Traditional protocols for distributed database management have high message overhead, lock or restrain access to resources during protocol execution, and may become impractical for some scenarios like real-time systems and very large distributed databases. In this paper we present the demarcation protocol; it overcomes these problems through the use of explicit arithmetic consistency constraints as the correctness criteria. The method establishes safe limits as "lines drawn in the sand" for updates and gives a way of changing these limits dynamically, enforcing the constraints at all times.