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Using a Quantum 984 HSBY System
108
840 USE 106 00 January 2003
While Your System Is Running
Constant Internal
Monitoring
After your Hot Standby system has been started and is running normally, it will
continue to function automatically. It constantly tests itself for faults and is always
ready to transfer control from the Primary to the Standby, if it detects a fault.
While the system is running, the primary CHS module will automatically transfer a
predetermined amount of state RAM to the Standby unit each scan. This ensures
that the Standby is ready to take control if needed.
If one or both of the links between the Hot Standby modules are broken, the Primary
controller will function as though no backup is available.
If the Primary controller fails, the Standby automatically assumes control of the
remote I/O network. If the Primary controller recovers from failure, it assumes
Standby responsibilities. If it cannot recover, it remains offline.
If the Standby controller fails, it goes offline. The Primary controller functions as a
stand-alone and continues to manage the I/O networks.