Replication Agreement; Data Consistency - Netscape DIRECTORY SERVER 6.0 - DEPLOYMENT Deployment Manual

Replication Agreement

Directory Servers use replication agreements to define replication. A replication
agreement describes replication between one supplier and one consumer. The
agreement is configured on the supplier server. It identifies:
• The database to replicate
• The consumer server to which the data is pushed
• The times that replication can occur
• The DN that the supplier server must use to bind (called the supplier bind DN)
• How the connection is secured (SSL, client authentication)

Data Consistency

Consistency refers to how closely the contents of replicated databases match each
other at a given point in time. When you set up replication between two servers,
part of the configuration is to schedule updates. With Directory Server 6.0, it is
always the supplier server that determines when consumer servers need to be
updated, and initiates replication.
Directory Server offers the option of keeping replicas always synchronized, or of
scheduling updates for a particular time of day, or day in the week. The advantage
of keeping replicas always in sync is obviously that it provides better data
consistency. The cost is the network traffic resulting from the frequent update
operations. This solution is the best in cases where:
• You have a reliable high-speed connection between servers
• The client requests serviced by your directory are mainly search, read, and
compare operations, with relatively few update operations.
In cases where you can afford to have looser consistency in data, you can choose
the frequency of updates that best suits your needs or lowers the affect on network
traffic. This solution is the best in cases where:
• You have unreliable or intermittently available network connections (such as a
dial-up connection to synchronize replicas).
• The client requests serviced by your directory are mainly update operations.
• You need to reduce the communication costs.
Introduction to Replication
Chapter 6 Designing the Replication Process 99