![]() The Distribution Agent copies the initial snapshot files from the snapshot folder and the transactions held in the distribution database tables to Subscribers. The Log Reader Agent monitors the transaction log of each database configured for transactional replication and copies the transactions marked for replication from the transaction log into the distribution database, which acts as a reliable store-and-forward queue. The Snapshot Agent prepares snapshot files containing schema and data of published tables and database objects, stores the files in the snapshot folder, and records synchronization jobs in the distribution database on the Distributor. Transactional replication is implemented by the SQL Server Snapshot Agent, Log Reader Agent, and Distribution Agent. For more information, see Transactional replication with Azure SQL Database and Azure SQL Managed Instance. Databases in Azure SQL Database can only be push subscribers for snapshot and transactional replication. ![]() However, transactional replication does offer options that allow updates at the Subscriber.Īzure SQL Managed Instance can be a publisher, distributor, and subscriber for snapshot and transactional replication. The Publisher or Subscriber is a non-SQL Server database, such as Oracle.īy default, Subscribers to transactional publications should be treated as read-only, because changes are not propagated back to the Publisher. The Publisher has a very high volume of insert, update, and delete activity. ![]() For example, if a row changes five times, transactional replication allows an application to respond to each change (such as firing a trigger), not simply the net data change to the row. The application requires access to intermediate data states. The application requires low latency between the time changes are made at the Publisher and the changes arrive at the Subscriber. You want incremental changes to be propagated to Subscribers as they occur. Transactional replication is typically used in server-to-server environments and is appropriate in each of the following cases: The data changes are applied to the Subscriber in the same order and within the same transaction boundaries as they occurred at the Publisher therefore, within a publication, transactional consistency is guaranteed. As soon as the initial snapshot is taken, subsequent data changes and schema modifications made at the Publisher are usually delivered to the Subscriber as they occur (in near real time). Transactional replication typically starts with a snapshot of the publication database objects and data. Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance
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