A root replica server is a replica server for the root domain. A subdomain master server is the master server for its domain. A subdomain replica server is a replica server for its domain. The only exception to this rule, a la UNIX, is that all servers of the root domain are clients of the root domain. There are equivalent commands to the file system commands that can be used.
Most client applications have a '-M' option, which requests service from the master only.
We recommend having no more than 10 replicas, otherwise to maintain too many more servers might degrade the performance that replicas are intended to provide. Sun Microsystems, Inc.