OSx Station Control 2-17SIMATIC PCS 7 OSx 4.1.2 Operator
2.5 Switch_Media Command
With two networks installed, the operator can change the currently selected
network for an OSx station from the Main Network to the Alternate
Network and vice versa. Do this to improve network throughput. The
system switches media for an OSx station automatically if the station
cannot communicate on the currently active network.
The operator can switch media for a station from any station on the system,
and only that station switches media. If the operator switches media for the
primary, the system automatically reverses the active and standby status
forallotherstations.
At any time, an OSx station can switch from one network to the other in its
communications with the primary. This can happen either by user command
or because of communications failure on the main network.
If a screen is displaying data that is obtained from the primary (such as a
trend display or report preview) during a media switch, and the station that
is switching networks is not the primary, that d isplay indicates an error.
Re-displaying or rereading the data corrects this, and the system now
transmits data over the second network.
This command is only selectable when all the following conditions are true.
• The selected station is an active, communicating station.
• The selected station is not undergoing a state transition.
• The role o f the selected station is not out_of_service.
• The main network of the selected station has not failed.
• The alternate network of the selected station has not failed.
• The local station has an active primary in its database.
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