Articles are tables of data, partitions of data, or database objects that are specified for replication. Each publication is a collection of articles from one database. This grouping of multiple articles makes it easier to specify a logically related set of data that is to be replicated together. In the Active Roles replication model, each article is a table of data.
SQL Server Agent hosts and schedules the agents used in replication, and provides a way to run replication agents. SQL Server Agent also controls and monitors several other operations outside of replication, including monitoring the SQL Server Agent service, maintaining error logs, running jobs, and starting other processes.
Replication Agents used with Microsoft SQL Server replication carry out the tasks associated with copying and distributing data. The Active Roles replication model employs the Snapshot Agent and Merge Agents.
The Snapshot Agent prepares schema and initial data files of published tables and stored procedures, stores the snapshot files, and records information about synchronization in the distribution database. In the Active Roles replication model, the Snapshot Agent runs at the Publisher.
The Merge Agent applies the initial snapshot to the Subscriber, and moves and reconciles incremental data changes that occur. Each Subscriber has its own Merge Agent that connects to both the Publisher and the Subscriber and updates both.
In the Active Roles replication model, the Merge Agents run continuously at the Publisher. Each Merge Agent uploads data changes from its Subscriber to the Publisher, and downloads data changes from the Publisher to the Subscriber.
Active Roles replication propagates the changes to configuration data to all replication partners whenever the data is modified on any one of replication partners. To achieve this goal, Active Roles relies on the merge replication provided by Microsoft SQL Server. For details on merge replication, refer to the content indexed under the Merge Replication topic in SQL Server Books Online.
This section briefly discusses the following elements of the Active Roles replication model: