Maintenance Manual________________________________________________________________
20 __________________________________________________________________ M210886EN-G
Duplicated System
A duplicated system contains two CDUs (CDU A and CDU B) which both
receive the same data from the sensors and perform the same parameter
calculations, independently of each other.
Both CDUs use the same configuration. They share and store the
operational parameters to ensure continuous operation in switch-over or
active CDU shutdown.
One of the CDUs is active (online) while the other is passive (hot standby/
offline). The active CDU provides the data for end-user applications.
The passive CDU monitors the active CDU. This way, the passive (hot
standby) CDU can replace the active CDU without delay if the active CDU
reports that a system program (ROASERVER.EXE) is missing. In such
situations, the system automatically switches the passive CDU as the
active CDU, and data processing can continue without any disruption to
system performance.
From the operational point of view there is no difference which one of the
CDUs is active. Switch-over and other functionalities are equal regardless
of which CDU is the active one.
Workstations and external systems have always active connection with the
active server. In switch-over situation, the workstations and external
systems may have to reconnect. This may cause a minor delay in data
transfer, but in typical LAN networks the delay is less than two seconds,
which is less than any meteorological parameter timeout period.
0312-006
Figure 4
Duplicated System
Field
Sensors
Data Collector
(Optional)
Serial/
LAN
Adapter
LAN
OWS
CDU A
CDU B
FWS
WV
RCM
Field
Sensors
Data Collector
(Optional)
Field
Sensors