The source database that becomes the target of the replication. All operations including a read and write operations are performed in this database.
A replicated database (replica) with the same contents as the master database. Changes in the master database are automatically reflected in the slave database. Unlike the master database, the slave database can be used for read operations only.
A server (also called a "primary server") that provides users with services. An active server provides all services including read and write by using the master database.
A server (called called a "secondary," "passive" or "failover" server) that provides services in place of an active server when it cannot provide services due to failure. A standby server provides a read service by using a slave database.
A feature that allows a standby server to automatically perform the failover and continue to provide services when the failure of an active server or the system running the active server is detected.
A feature that allows the automatically-restored active server to resume services after the failover when it is restored to the original state.
A feature that allows services to be provided continuously without failback even when the failure in the previous active server is restored.
An essential element for providing HA features. This feature checks the availability of important resources comprising the system such as data, application programs and services, and provides failover, failback and monitoring functionalities.
Building the system with duplicate server hardware to provide HA functionalities. Two methods are used: to allow the standby server to perform the functionality of the active server upon failure (Active-Standby, see the figure below) and to build a duplicate system that provides services while additionally performing the roles of the server upon failure (Active-Active).
An architecture with multiple database servers so that the service will be provided without interruption even when a database failure occurs. If a failure occurs in an active database providing a service, a standby database with the same data can provide the service.
An architecture built with broker multiplication so that a service can be provided without interruption by another broker when a failure occurs in a certain broker. In addition, each broker can have different characteristics as described below.
A feature that allows the transaction log created in an active server to be sent in real time to one or more standby servers so that the same log will be recorded in all the servers.