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Replication in SQL Server 2008:

Replication uses a publishing industry terminology, which include Publisher, Distributor, Subscribers, publications, articles, and subscriptions.
• Publisher produces publications
• Publication contains articles
• The publisher either distributes publications by himself or uses separate distributor.
• Subscribers receive publications to which they have subscribed.
SQL Server replication includes the ability for a Subscriber to make updates and for a Publisher to send out incremental changes to the articles in a publication.
There are few replication processes/agents that are responsible for copying and moving data between the Publisher and Subscribers.
SQL Server Replication
The Publisher is a database instance that makes data available to other locations/instances through replication. The Publisher can have one or more publications defining a logically set of objects and data that is replicated.
The Distributor is a database instance that acts as a store for replication specific data associated with one or more Publishers. Each Publisher is associated with a single database (known as a distribution database) at the Distributor. The distribution database stores replication status data, metadata about the publication. A single database server instance can act as both the Publisher and the Distributor which is called as a local Distributor. When the Publisher and the Distributor are configured on separate database server instances then it is called as a remote Distributor.
A Subscriber is a database instance that receives replicated data. A Subscriber can receive data from multiple Publishers and publications. Depending on the type of replication, the Subscriber can also pass data changes back to the Publisher or republish the data to other Subscribers.
An article identifies a database object that is included in a publication. A publication can contain different types of articles, including tables, views, stored procedures, and other objects. When tables are published as articles, filters can be used to restrict the columns and rows of the data sent to Subscribers.
A publication is a collection of one or more articles from one database. The grouping of multiple articles into a publication makes it easier to specify a logically related set of database objects and data that are replicated as a unit.
A subscription is a request for a copy of a publication to be delivered to a Subscriber. The subscription defines how the publication will be received. There are two types of subscriptions: push and pull

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