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One of the many powerful features of SQL Server is its ability to carry out data replication. This process involves distributing and synchronizing data from different databases to improve data availability. This blog post is aimed at providing a clear understanding of how SQL Server carries out data distribution with examples of SQL code included.
Understanding SQL Server Replication
SQL Server Replication is a set of technologies for managing and distributing data and database objects between databases in a network. It allows you to not only manage but also to copy, distribute data and database objects from one database to another and then synchronize them to maintain consistency. There are three types of SQL server replication which include snapshot, transactional, and merge replication.
1. Snapshot Replication
Snapshot replication distributes data as it appears at a specific point in time and does not monitor for updates to the data. When synchronization occurs, the entire snapshot is generated and sent to the Subscribers.
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-- Creating a snapshot EXEC s<a href="mailto:p_addpublication @publication" >p_addpublication @publication</a> = 'snapshot_publication', @description = 'publication of snapshot data.', @sync_method = 'character', @retention = 0, @allow_push = true, @allow_pull = true, @allow_anonymous = true, @enabled_for_internet = false, @snapshot_in_defaultfolder = true, @compress_snapshot = false, @ftp_port = 21, @allow_subscription_copy = false; GO |
2. Transactional Replication
Transactional replication starts with a snapshot of the publication database objects and data. Once the initial snapshot is taken, incremental changes made at the Publisher are tracked and delivered to the Subscriber as they occur.
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-- Creating a transactional replication EXEC s<a href="mailto:p_addpublication @publication" >p_addpublication @publication</a> = 'transactional_publication', @description = 'publication of transactional data.', @sync_method = 'concurrent', @retention = 0, @allow_push = true, @allow_pull = true, @allow_anonymous = true, @enabled_for_internet = false, @compress_snapshot = false, @ftp_port = 21, @allow_subscription_copy = false; GO |
3. Merge Replication
Merge Replication, like transactional replication, starts with a snapshot of the publication database objects. Data changes and schema modifications made at the Publisher and Subscribers are tracked with triggers.
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-- Creating a merge replication EXEC s<a href="mailto:p_addpublication @publication" >p_addpublication @publication</a> = 'merge_publication', @description = 'publication of merge data.', @sync_method = 'native', @retention = 14, @allow_push = true, @allow_pull = true, @allow_anonymous = true, @enabled_for_internet = false, @compress_snapshot = false, @ftp_port = 21, @allow_subscription_copy = false; GO |
In conclusion, SQL Server replication allows databases to work together more seamlessly, efficiently offering data availability, disaster recovery, and load balancing benefits. It is a technique that, when leveraged properly, can hugely benefit DBAs and the organizations they work for.