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5.1 Basic Concept of Redundant System
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REDUNDANT SYSTEM FUNCTIONS
CHAPTER5 REDUNDANT SYSTEM FUNCTIONS
This chapter explains the redundant system functions.
5.1 Basic Concept of Redundant System
A redundant system consists of two basic systems, each of which includes a power supply
module, CPU module, main base unit and network module.
To configure a redundant system, connect the basic systems on which above modules are
mounted with a tracking cable.
(Please refer to Section 2.1 for system configuration.)
(1) Determination of System A and System B
In a redundant system, one basic system is called "System A", and the other, "System
B", to identify each of the two systems connected with a tracking cable.
Please refer to Section 5.1.1 for determination of system A and system B.
(2) Control System and Standby System
In a redundant system, the CPU module of either system performs operations and
controls the redundant system.
The other system, which is for backup, does not perform operations.
The controlling system is referred to as "Control system", and the backup system,
"Standby system".
Please refer to Section 5.1.2 for details on the control system and standby system.
(3) Switching Between the Control System and Standby System
If a fault occurs in the control system, the backup system takes over the system
control and continues the operation.
Please refer to Section 5.3 for switching between the control system and standby
system.
(4) Consistency Check between Control System and Standby System
A redundant system conducts "Consistency check between Systems A and B" to
check if the control system and standby system are consistent so that control
continues without the system going down when system switching occurs.
Refer to Section 5.1.4, for consistency check between systems A and B.
Diagram 5.1 Redundant System Configuration
System A - Control System
System B - Standby System
Tracking cable