Database replication is the process of copying data from one database to another in order to ensure that the data is available in more than one location. The goal of replication is to provide high availability, disaster recovery, and load balancing.
In a replication scenario, there is typically one primary database that is responsible for processing transactions, and one or more secondary databases that are used for read-only purposes. When a write operation is performed on the primary database, the change is propagated to the secondary databases so that they are kept in sync.
There are two main types of replication: master-slave replication and master-master replication.
In master-slave replication, the primary database (master) sends updates to one or more secondary databases (slaves). The slaves are read-only and cannot be used for write operations. This approach is typically used to distribute read operations across multiple servers in order to improve performance.
In master-master replication, multiple databases act as both masters and slaves. Each database can receive updates from other databases and can send updates to other databases. This approach is typically used to provide high availability and disaster recovery capabilities.
Replication can be performed either synchronously or asynchronously. In synchronous replication, the primary database waits for an acknowledgement from the secondary database before committing the transaction. This ensures that the data is consistent across all databases, but it can result in increased latency and decreased throughput. In asynchronous replication, the primary database does not wait for an acknowledgement from the secondary database before committing the transaction. This can result in faster write operations, but it can also result in data inconsistencies if there are network issues or other failures.