Sunday, June 3, 2007

Question 32

Which is the appropriate description of a dual system?

a) Two systems, both performing the same processing, are installed, and processing accuracy is checked by verifying the results of processing on both systems. If one of the systems fails, processing continues under a degradation mode using only the other system.
b) A main system for performing online processing, and a standby system which performs batch processes, etc. while it stands by are installed. If the main system fails, online processing is restarted by switching the system after reloading the online programs into the standby system.
c) The online processing programs of the main system are loaded onto the standby system before it begins to stand by. If the main system fails, an immediate switching is made to the standby system and the processing continues.
d) A single computer is equipped with each pair of processors, memories, channels, power sources, etc. so that processing can continue even if one device of any pair fails.


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