Red Hat Directory Server 8.0 Administrator's Guide

Managing Replication
Replication is the mechanism by which directory data is automatically copied from one Red Hat
Directory Server instance to another; it is an important mechanism for extending the directory
service beyond a single server configuration. This chapter describes the tasks to be performed
on the master and consumer servers to set up single-master replication, multi-master
replication, and cascading replication.
1. Replication Overview
Replication is the mechanism by which directory data is automatically copied from one Directory
Server to another. Updates of any kind — entry additions, modifications, or even deletions —
are automatically mirrored to other Directory Servers using replication. This section contains
information on the following replication concepts:
• Section 1.1, “What Directory Units Are Replicated”
• Section 1.2, “Read-Write and Read-Only Replicas”
• Section 1.3, “Suppliers and Consumers”
• Section 1.4, “Changelog”
• Section 1.5, “Replication Identity”
• Section 1.6, “Replication Agreement”
• Section 1.7, “Compatibility with Earlier Versions of Directory Server”
1.1. What Directory Units Are Replicated
The smallest unit of of the directory which can be replicated is a database. This means that one
can replicate an entire database but not a subtree within a database. Therefore, when creating
the directory tree, consider any replication plans as part of determining how to distribute
information.
Replication also requires that one database correspond to one suffix. This means that a suffix
(or namespace) that is distributed over two or more databases using custom distribution logic
cannot be replicated. For more information on this topic, see Section 2, “Creating and
Maintaining Databases”.
1.2. Read-Write and Read-Only Replicas
A database that participates in replication is called a replica. There are two kinds of replicas:
read-write or read-only. A read-write replica contains master copies of directory information and
can be updated. A read-only replica services read, search, and compare requests, but refers all
update operations to read-write replicas. A server can hold any number of read-only or
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