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DBMS | Data Replication and its Types

In this tutorial, we are going to learn about the data replication and its types and some of terms used with data replication in DBMS.
Submitted by Anushree Goswami, on July 07, 2019

Data replication as its name suggests is a process in which data is copied to different locations, to one site or node, either computers or servers, in order to surge the improvement of the data. It is aimed for the improvement of the data as well as to speed up the evaluation of the queries. It is a very simple structure to perform. The data is copied from the one location to another location simply to decrease the inconsistency of the data around the server.

You can simply think about data that is being written in one dataset and then copied and transferred to multiple locations. It helps in such a way that whenever a user at a particular location required that data then he/she may get that data from that location itself and does not require to go to the main server or location or computer to find and access that data. In this way, it becomes easier for the user to retrieve the information.

Data replication is an ongoing process. The duplication of data is done in a consistent manner in a given interval of time and is synchronized with the source. Although the data is present everywhere, a particular relation is placed at any one location or computer or server.

Before getting into the depth of Replication, let us get familiar with few terms –

Publisher: Publisher is the source of the database; it is from here that the original data get replicated to other location.

Subscriber: Subscriber is a destination database where the replicated data is sent. For a single publisher, there can be many numbers of subscribers.

Distributor: Distributor act as a medium which is used to distribute the transaction over the subscriber database.

Types of Data Replication

There are mainly 5 types of Data Replication

  1. Snapshot Replication
  2. Transactional Replication
  3. Merge Replication
  4. Heterogeneous Replication
  5. Peer to Peer Transactional Replication

1) Snapshot Replication

In Snapshot Replication, the whole relation at a particular time at the given location is replicated wholesome to other location without any change. It is helpful for those transactions where the whole relation is required in order to perform any query. It is helpful in the initial synchronization when the data is changed less frequently between publisher and subscriber.

Data Replication (1) in DBMS

Image source: https://filedb.experts-exchange.com/incoming/2016/05_w22/1099800/IC171003.gif

2) Transactional Replication

In Transactional Replication, whatever changes have been done in the relationship that is only sent to multiple locations. In this replication, data flow takes from the publisher to the subscriber side. Other all data remains as such and no changes or transaction is made for those data. It is quite faster than Snapshot Replication as only the modified data is needed to be sent from one place to another. It is best suited for the server-to-server environment in order to maintain the consistency of the data at every place.

Data Replication (2) in DBMS

Image source: https://docs.microsoft.com/en-us/sql/relational-databases/replication/transactional/media/trnsact.gif?view=sql-server-2017

3) Merge Replication

In merge replication, the data transfer takes place from both sides of the publisher and subscriber. Data from both sides are combined to make a single database. It is very complex as both sides are making changes in the database. It is mainly used in the server-to-client environment.

Data Replication (3) in DBMS

Image source: https://docs.microsoft.com/en-us/sql/relational-databases/replication/merge/media/merge.gif?view=sql-server-2017

4) Heterogeneous Replication

In Heterogeneous Replication, the user gets access to other database products as well which means the data servers that are provided by the other vendors. The data replication takes place in between the heterogeneous data servers. There is an ECD database gateway in between the replicate server and replicate the database through which the transfer occurs.

Data Replication (4) in DBMS

Image source: http://infocenter.sybase.com/help/topic/com.sybase.infocenter.dc36924.1571/doc/image/penamu1276666305506_11-san1276287862704.image

5) Peer to Peer Transactional Replication

In Peer to Peer Transactional Replication, multiple servers are involved and they are termed as nodes. Every node here acts as publisher and subscriber both. The data is sent and received through the particular node and the data is synchronized in between.

Data Replication (5) in DBMS

Image source: https://docs.microsoft.com/en-us/sql/relational-databases/replication/transactional/media/repl-multinode-01.gif?view=sql-server-2017








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