The discrete pieces of data being sent to another server or database. An article will represent either an entire table or a subset of that able.

Subscription

The group of data that a server or database will receive. This can be one or more publications.

Push subscription

The publishing server will periodically push transactions out to the subscribing server or database. The publisher in this method drives the replication process.

Pull subscription

The subscribing server will periodically connect to the distribution database and pull information. The subscriber in this method drives the replication process.

Synchronize

The process that initially ensures that both publisher and subscriber contain the same data.

Log reader

An internal SQL Server process that reads the transaction logs on a database that is publishing data to determine if the data needs to be replicated.

Distribution database

During the replication process, the Log Reader monitors the transaction log on databases configured for publishing. When the Log Reader encounters a transaction that matches an article, the transaction is copied to the distribution database along with information concerning where to send the data. The distribution database then performs the process of sending the data to each of the subscribers. Once all of the subscribers have notified the distributor that the transaction has been accepted, the transaction is removed from the distribution database. This is a highly volitile database that you will want to watch carefully for corruption, space, or connectivity problems.

Replication Topologies

Version 7.0 adds support for numerous additional topologies. Currently there are eight replication topologies supported by Microsoft SQL Server. Five of these existed in previous versions of SQL Server with three more being added in version 7.0. The eight topologies represent a business model for the way replication is supposed to distribute data. These topologies are as follows:

• Central publisher
• Central subscriber
• Central distributor
• Central publisher with remote distributor
• Publishing subscriber
• Anonymous
• Merge
• Bi-directional

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