This document describes a log-keeping mechanism designed to support Global Garbage Detection on Amadeus. This log-keeping mechanism maintains, on a per site basis, a conservative approximation of the actual root set for that site. Exchanges of object references across site boundaries are logged on a per cluster basis to cope with the dynamic nature of the overall object graph. Clustering also determines the granularity of the information logged. Furthermore, this mechanism proceeds lazily, that is, it does not require either any additional messages to be exchanged (and thus does not cause any race condition), nor trigger any object fault which would not otherwise have occurred. This mechanism makes it possible to implement at a reasonable cost, a higher level comprehensive, although scalable, Global Garbage Detection algorithm.