The Publishing/Subscribing Metaphor

SQL Server 6.0 replication terminology is based on a publishing/subscribing metaphor:

• When data is made available for replication, it is published. The server that contains the source database and makes the data available for replication is called the publication server or publisher.
• An article is the basic unit of replication. It contains data originating from a single table that has been marked for replication. Each article must belong to a publication.
• A publication is a collection of articles. One or more articles can belong to a publication. One or more publications can be created from each user database on a publication server.

  Note that all articles within a publication are guaranteed to be initially synchronized as a single logical unit. This helps to maintain integrity relationships originating from the underlying tables.

• When a server requests a publication, it becomes a subscription server or subscriber. A subscriber can subscribe to some or all available publications and to some or all articles within a publication.

Replicated data moves in only one direction ¾ from the publication server to the subscription servers. You will usually treat replicated data residing in destination tables on subscription servers as read-only. (Note that this means the data should be treated as read-only for the users of the subscription databases. Do not set the Read Only database option, or that subscription database will be unable to receive replicated data.)

This is not so limiting as it might at first sound, since each server can act as both subscriber and a publisher and secondary copies of data can be locally processed on the subscriber. For examples of publishing subscribers and of secondary processing of data, see Chapter 15, Advanced Replication.