Replication OverviewChapter 8 Managing Replication 303Supplier/ConsumerA server that holds a replica that is copied to a replica on a different server is calleda supplier for that replica. A server that holds a replica that is copied from adifferent server is called a consumer for that replica. Generally, the replica on thesupplier server is a read-write replica and the one on the consumer server is aread-only replica. There are exceptions to this statement:• In the case of cascading replication, the hub supplier holds a read-only replicathat it supplies to consumers. For more information, refer to “CascadingReplication,” on page 310.• In the case of multi-master replication, the masters are suppliers andconsumers for the same read-write replica. For more information, refer to“Multi-Master Replication,” on page 307.In Directory Server, replication is always initiated by the supplier server, never bythe consumer. This operation is called supplier-initiated replication. It allows youto configure a supplier server to push data to one or more consumer servers.Earlier versions of the Directory Server allowed consumer-initiated replication,where you could configure consumer servers to pull data from a supplier server.ChangelogEvery supplier server maintains a changelog. A changelog is a record thatdescribes the modifications that have occurred on a replica. The supplier serverthen replays these modifications to the replicas stored on consumer servers or toother suppliers, in the case of multi-master replication.When an entry is modified, a change record describing the LDAP operation thatwas performed is recorded in the changelog.In Directory Server, the format of the changelog has changed. It is now onlyintended for internal use by the server. If you have applications that need to readthe changelog, you need to use the Retro Changelog Plug-in for backwardcompatibility. For more information, refer to “Using the Retro Changelog Plug-in,”on page 357.
