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 Architecture of a Hot Standby System 

A hot standby system consists of a master component and one or more standby components. On the outside, the hot standby system behaves like any normal database instance. Within the cluster system, the individual components communicate with one another using internal local addresses.

If you want to access the hot standby system from outside the cluster, you need the common name of the database instance and the official name of the component, on which the database runs. If the master component is not available, this official name is transferred to the standby component, which adopts the functions of the master component.

The standby components are in STANDBY operational state , which is a status between ADMIN state and ONLINE state. In STANDBY state, standby component is not a real instance. It only becomes a real instance if the master instance is not available, in which case the standby component adopts the function of the master instance.

Master components and standby components each have their own independent data areas. However, they both access the same log area. Standby components only have read access to this log area.

You must mirror the log area to protect against hardware errors.

Unlike hot standby systems, standby databases have separate log areas for all instances.

Both master components and standby components have their own kernel, caches, X server, DBM server, and so on, but they use the same database parameters.

See also:

Synchronizing Master Components and Standby Components

 

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