We propose an instance of RPD called RPD-SD in which the shared submap contains entries for only objects that are shared. RPD-SD can be implemented as a variant of CSD in which the role of the mapping server is to identify shared documents and propagate updates to the submap, rather than to respond to synchronous queries. As in CSD, the mapping server maintains an authoritative copy of the complete global directory. Each proxy periodically contacts the mapping server and passes a stream of URLs fetched or discarded at that proxy. The mapping server responds with a stream of updates to the submap replica at that proxy.
Percentages are relative to all references in the trace.
Figure 8 shows a detailed breakdown of all shared document references. We partition the shared references into several subcategories. For every shared object, the first reference is always a compulsory miss, and the first-shared reference is the access that marks it as shared. A repeat shared reference is a further access to an object by a client who has already accessed it before. This can be satisfied, for example, by setting an interval of 2 minutes for the cache to mapping server update rate, and likewise for the mapping server to replicated submap.