Directory servers are responsible for the following tasks:
Persistence of data and serving client requests
Forwarding changes to specific replication servers
When a change is made on a directory server, that server forwards the change to a selected replication server. The replication server then replays the change to other replication servers in the topology, which in turn replay the change to all other directory servers in the topology.
Each directory server contains the following items:
A list of the suffix DNs to be synchronized
For each suffix DN, a list of replication servers to connect to
Applications should typically perform reads and writes on the same directory server instance. This prevents those applications from experiencing consistency problems due to loose consistency.