Replication is the process of copying updates between OpenDJ directory servers such that all servers converge on identical copies of directory data. Replication is designed to let convergence happen over time by default. [6] Letting convergence happen over time means that different replicas can be momentarily out of sync, but it also means that if you lose an individual server or even an entire data center, your directory service can keep on running, and then get back in sync when the servers are restarted or the network is repaired.
Replication is specific to the OpenDJ directory service. Replication uses a specific protocol that replays update operations quickly, storing enough historical information about the updates to resolve most conflicts automatically. For example, if two client applications separately update a user entry to change the phone number, replication can work out which was the latest change, and apply that change across servers. The historical information needed to resolve these issues is periodically purged to avoid growing larger and larger forever. As a directory administrator, you must ensure that you do not purge the historical information more often than you backup your directory data.
Keep server clocks synchronized for your topology. You can use NTP for example. Keeping server clocks synchronized helps prevent issues with SSL connections and with replication itself. Keeping server clocks synchronized also makes it easier to compare timestamps from multiple servers.
[6] Assured replication can require, however, that the convergence happen before the client application is notified that the operation was successful.
