Red Hat Directory Server 8.0 Administrator's Guide

read-write replicas.
1.3. Suppliers and Consumers
A server that holds a replica that is copied to a replica on a different server is called a supplier
for that replica. A server that holds a replica that is copied from a different server is called a
consumer for that replica. Generally, the replica on the supplier server is a read-write replica,
and the one on the consumer server is a read-only replica, with two exceptions:
•
In the case of cascading replication, the hub server holds a read-only replica that it supplies
to consumers. Section 2.3, “Cascading Replication” has more information.
• In the case of multi-master replication, the masters are both suppliers and consumers for the
same information. For more information, see Section 2.2, “Multi-Master Replication”.
Replication is always initiated by the supplier server, never by the consumer (supplier-initiated
replication). Supplier-initiated replication allows a supplier server to be configured to push data
to multiple consumer servers.
1.4. Changelog
Every supplier server maintains a changelog, a record of all changes that a supplier or hub
needs to send to its consumers. A changelog is a special kind of database that describes the
modifications that have occurred on a replica. The supplier server then replays these
modifications to the replicas stored on consumer servers or to other suppliers, in the case of
multi-master replication.
When an entry is modified, a change record describing the LDAP operation that was performed
is recorded in the changelog.
In Directory Server, the changelog is only intended for internal use by the server. For other
applications to read the changelog, use the Retro Changelog Plug-in, as described in
Section 16, “Using the Retro Changelog Plug-in”.
1.5. Replication Identity
When replication occurs between two servers, the replication process uses a special entry,
called the replication manager entry, to identify replication protocol exchanges and to control
access to the directory data. The replication manager entry, or any entry used during replication,
must meet the following criteria:
• It is created on the consumer server (or hub) and not on the supplier server.
• Create this entry on every server that receives updates from another server, meaning on
every hub or dedicated consumer.
• When a replica is configured as a consumer or hub (a replica which receives updates from
Chapter 8. Managing Replication
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