Chapter 5 – Test Management
Availability – ISTQB Definition
Last Updated: July 12, 2026 · SoftwareTestPilot QA Team
Official ISTQB Definition
The degree to which a component or system is operational and accessible when required for use.
In simple words
Percentage of time the system is up and usable — the 'nines' number.
Exam tip
Typical SLAs quote 99.9% (three nines) up to 99.999% (five nines).
Related terms
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