# What is Availability? – Definition, Elements, Types and More

## Availability Definition

The concept of availability is used in various fields and spheres to refer to the possibility that something, a product or a phenomenon, is available to be made, found, or used. Availability means that that thing or merchandise, for example, soap, is available for use. That it is convenient means in turn that one can dispose of it since it is accessible, within reach, or simply because it is possible to do so.

## Why is “availability” so important today?

The reason why [availability] today is a vital measure of the quality of an IT system or IT service is, of course, the importance that corporate IT has today in general for running a business. Many business processes (production, sales, logistics, project management, etc.) are no longer feasible without IT.

Often, a failure of an IT system equates to a shutdown (at least in parts) of the business. It leads to costly consequences in terms of lost production or sales. Another reason for the central importance of the topic “availability” lies in the changing role of the IT department. And this happens in many companies.

## Elements

Availability depends on the combined aspects of reliability, maintainability, and logistics with an entity. It is therefore not influenced by phenomena that originate outside the substance even though it appears inside it.

Contrary to what some say, by examining the calculation algorithms, the availability, in its various forms, ultimately depends on the unavailability times caused by the stops. While the frequency of the stops has no impact (as instead, it has in the reliability calculation) since the numerator and denominator of the formulas indicated above is simplified and therefore eliminated.

Then anyone can easily see the appropriate replacing indicators with their respective calculation formulas.

## Mathematical and percentage formulas of [availability]

Mathematical formula: availability = total time – downtime/full time.
Percentage: availability = total time – downtime/full time × 100%.

In calculating [availability], reference, they divide into three different indicators:

### Technical availability

Formulation:

Technical availability = MTTF / ( MTTF + MTTR )

In fact, the index measures the [Availability] resulting from the failure events and from the System’s ability to perceive such status, to report it, to face it and resolve it, that is, it takes into account both the repair time and the logistic accessory times (waiting for maintenance, waiting for spare parts, testing, etc.).

### Operational [availability]

Formulation:

Operational [availability] = MTBM / ( MTBM + MDT )

The adjective “Operative” underlines the fact that all the “physical” factors that contribute to unavailability are taken into account, whether induced by maintenance in its various forms or induced by the specification of the Process/Project, for example the technical times of preparation.

### Intrinsic availability

Formulation:

Intrinsic availability = MTTF / ( MTTF + MRT )
The adjective “intrinsic” underlines the fact that maintenance logistics did not take into account, but only the technical repair time of the entity (” intrinsic,” in particular).