Schneider Electric 840 USE 106 0 manual While Your System Is Running

Using a Quantum 984 HSBY System

While Your System Is Running

Constant Internal After your Hot Standby system has been started and is running normally, it will

Monitoring 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.

108 840 USE 106 00 January 2003