ITPEC FE Morning April 2019 Question 14
Which of the following is the most appropriate description of a dual system?
Explanation
Two systems do the same processing and collate the results — a dual system runs both computers on the same work and compares their output.
Because both systems process every transaction, comparing the results detects errors, and when one system fails the other continues alone in degraded operation. A duplex system, by contrast, has one active system and one standby system that takes over only after a failure.
Answer (c)
Why not others:
- •(a) — a standby system loaded with the online program and ready to take over at once is a hot standby, a form of duplex system
- •(b) — duplicating the processor, memory, channels and power supply inside one machine so it runs through any single failure describes a fault-tolerant computer
- •(d) — an active system for online work with the standby system doing batch work until a failure is a duplex system
Key rule: Dual system = both systems run the same processing and cross-check each other; duplex system = one active, one standby that takes over on failure.
System Component · AI-written, may contain errors
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