A communications system and method include an efficient cache invalidation technique which allows a computer to relocate and to disconnect without informing the server. The server partitions the entire database into a number of groups. The server also dynamically identifies recently updated objects in a group and excludes them from the group when checking the validity of the group. If these objects have already been included in the most recent invalidation broadcast, the remote computer can invalidate them in its cache before checking the group validity with the server. With the recently updated objects excluded from a group, the server can conclude that the cold objects in the group can be retained in the cache, and validate the rest of the group.