Prioritized replication can be used when there is a strong business requirement to have tighter consistency for replicated data on specific attributes. In 5.x version of Directory Server, updates were replicated in the order in which they were received. With prioritized replication, you can specify that updates to certain attributes take precedence when they are replicated to other servers in the topology.
Prioritized replication provides the following benefits:
Improved security. Prioritized replication is used by default for account lockout. Imagine for example that an employee leaves your organization, and you lock the employee's account. To ensure that the employee cannot log in to a remote server to which the account lockout has not been replicated, account lockout changes are replicated before other changes are replicated.
Improved consistency. Directory Server replication is loosely consistent. With prioritized replication, you can assure stronger consistency for certain attributes that are considered important in your organization.