Replication is the capability to copy data and changes to that data from one database to another. FIG. 1 illustrates an overview of conventional transactional replication. A Publisher 200 is a server or database that sends its data to another server or database. The Publisher 200 may contain publication/publications that are a collection of one or more articles that are sent to a subscriber server or database. In transactional replication, an article is what is to be replicated, and may be an entire table, select rows from a table, specified columns from a table or a stored procedure.
A Distributor 202 manages the flow of data through the replication system. The distributor 202 contains a distribution database that tracks the changes (to publications) that need to be replicated from publishers 200. A publisher 200 may act as its own distributor 202, or a remote database server can be used to hold the distribution database.
A Subscriber(s) 204 is a server or database that receives data from the publisher 200 or other database. A subscription is the group of data that a server or database 204 will receive. This can be one or more publications. There are push and pull subscriptions. A push subscription is subscription when the publishing server will periodically push transactions out to the subscribing server or database. A pull subscription is subscription when the subscribing server will periodically connect to the distribution database and pull information.
In conventional transactional replication, replicated commands are typically applied through a single connection 203 at the subscriber, as shown in FIG. 1. While a single connection ensures the transactions will be applied at the subscriber in the exact order as the transactions occur on the publisher, there are performance losses with this method, especially when requests are from a heavily loaded publisher.
In addition, conventional replication technique utilizes triggers when an insert, update, or delete operation occurs, to keep track of changes made to published table. This adds additional overhead to Publisher 200 because of the triggers. Thus, there is a need for increasing the performance of transactional replication systems, while reducing overhead costs and ensuring that transactions are properly applied at the subscriber. The present invention provides such a solution.