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Bài giảng Cơ sở dữ liệu nâng cao Chapter 6 Data replication. Những nội dung chính được trình bày trong chương này gồm có Overview of replication, replication scenario, replication types. Mời các bạn cùng tham khảo.
Data Replication Overview of Replication SQL Server replication is a set of technologies for: copying and distributing data and database objects from one database to another Then, synchronizing between databases to maintain consistency Types of replication: Snapshot replication Transactional replication Merge replication Peer – to – peer replication Oracle Publishing replication All of these types rely on a number of standalone programs – agents Replication Scenario Replication is analogous to the publishing industry Article: a database object that you want to replicate; it can be a Table, View, or Store procedure, or other objects Publication: A collection of articles One article can be in one or more publications Publication can be treated as a logical grouping for the articles For example: To replicate only the employee master data, you can include employee table article, address article, and any other relevant views to the publication Replication Scenario Subscription: A request for a copy from the publication Define where to receive the publication, what the frequency for the receiving is, … Publisher A database instance that holds publications for other database instances to receive There can be several different types of publication in one publisher Replication Scenario Distributor: Each publisher has a distributor to store replication status data, and metadata about the publication Sometimes the distributor acts as a data queue for data moving from the publisher to the subscribers and vice versa There are two types of distributors: local and remote Local distributor is where the publisher and distributor are in one database server instance Subscriber: A database instance that receives replicated data from the publisher In some replication types the subscriber also passes data to the publisher Replication Types Snapshot: Distribute data as it appears in the publisher at a specific moment of time Whenever the Subscriber called for subscription, it will send the snapshot of the current Publisher and send it to the Subscribers Limitations for using Snapshot Replication: Replicating a small volume of data Infrequently changing data Snapshot replication does not require primary article tables Replication Types Components in Snapshot Replication: Two agents are used in Snapshot Replication, snapshot and distribution Snapshot Agent: A shared agent for all replication types The snapshot agent’s job is to generate data scripts for the objects you are replicating These scripts are written to a folder in the file system called a snapshot folder Distribution Agent: This agent will read from a snapshot folder and distribution database to propagate to the subscriber end Replication Types Transactional: The most used replication type The most valuable feature of the transactional replication is the ability to replicate incremental changes rather than applying the all-data set Use transactional log to generate transactions for replication Here are the scenarios where you can use transactional replication: Replicate huge volumes of data For real-time application Replicate data between non-SQL Server databases Replication Types Transactional: The most used replication type The most valuable feature of the transactional replication is the ability to replicate incremental changes rather than applying the all-data set Use transactional log to generate transactions for replication Here are the scenarios where you can use transactional replication: Replicate huge volumes of data For real-time application Replicate data between non-SQL Server databases Replication Types Peer-to-Peer Replication Peer-to-peer replication is an option with transactional replication All nodes in a peer-to-peer replication topology subscribe and publish from and to all other nodes A transaction originating at one node will be replicated to all other nodes, but not replicated back to originator This replication model is intended for use in applications to have multiple databases or database servers participating in a scale-out solution Replication Types Merge Replication Start from the initial snapshot Afterward, changes at both publisher and subscriber(s) are tracked with triggers Subsequent data changes and schema modifications made at the Publisher and Subscribers are tracked with triggers The Subscriber synchronizes with the Publisher when connected to the network and exchanges all rows that have changed between the Publisher and Subscriber since the last time synchronization occurred ... Replicate data between non-SQL Server databases Replication Types Peer-to-Peer Replication Peer-to-peer replication is an option with transactional replication All nodes in a peer-to-peer replication. .. maintain consistency Types of replication: Snapshot replication Transactional replication Merge replication Peer – to – peer replication Oracle Publishing replication All of these types... one database server instance Subscriber: A database instance that receives replicated data from the publisher In some replication types the subscriber also passes data to the publisher Replication