HA refers to high availability, and to minimize the frequency and time that functions and services provided by the system are stopped or interrupted. Also, a system (HA) or a system configuration(HA configuration) in which such measures are taken may be simply referred to as HA.
In a narrow sense, multiple computers are bundled and operated in an integrated manner, and clustering technology that makes them behave as if they are one computer prevents the whole from stopping even if one stops. It refers to the state(HA cluster).
In a broad sense, it includes all techniques such as redundancy and multiplexing (duplexing) of equipment and systems, data replication and automatic switching, and a hot standby configuration and cold standby configuration in which two systems of the same system are prepared in some cases, HA may be promoted using database replication and the like (and their combination).
