ISTQB Certified Tester Foundation Level v4.0 — Question 82

Which sequence of state transitions is INCORRECT in accordance with the following description?

To provide for disaster recovery a system (designated as A) has been provided with a backup system (designated as B). Only one of them can be active at a time. When A goes down, В becomes active. When A comes back up then В becomes inactive and A becomes active again. However, when A is down and В also goes down then a message is sent to the system administrator. After this once A comes back up, A becomes active or if В comes up then В becomes Active.

Answer options

• A. A is active and В is inactive A goes down. В becomes active then В goes down. A is made active
• B. A comes up when В is active and A was down Now A becomes active and В becomes inactive
• C. A is active and В is inactive then A goes down В becomes active
• D. A and В are both down then A and В both come back up at the same time A should become the active system and В should be inactive

Correct answer: D

Explanation

The correct answer is D because the system description states that only one system can be active at a time. When both A and B come back up simultaneously, it contradicts the operational rules provided. Options A, B, and C all follow the correct behavior of the systems transitioning between active and inactive states.