Techniques are provided for managing replicated data items in a cluster of
shared nothing nodes. The techniques include synchronously propagating
changes to one or more replicas, while asynchronously propagating changes
to the remaining replicas. Because the replicas to which the change is
synchronously replicated may be a relatively small percentage of the
total number of replicas, the overhead associated with performing an
update is reduced. The process of selecting which nodes are involved in
the synchronous update operation may take into account a variety of
factors, including which replicas are available at the time the update
operation is being performed.