Siemens SIMATIC PCS 7 OSx, Operator'S Manual

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OSx Station Control
2-14
SIMATIC PCS 7 OSx 4.1.2 Operator
Role_Change Command (continued)
OSx stations change roles automatically under the following conditions.
•
When you change a station to the primary or backup role, the station
that previously held the role automatically changes to the normal role.
The replacement station changes to the newly selected role (primary or
backup). This process normally occurs very quickly, but there is a brief
period when the two stations have the same role. If an error occurs
during the process, both stations retain their previous roles.
•
When the primary loses contact with the other OSx stations, its role
changes automatically to out_of_service and it enters the Failed state.
Limited communication with the control nodes may still be possible if
the ethernet communications layer is still functioning.
Keep the following considerations in mind concerning automatic role
changes.
• If an OSx station loses contact with the primary, that station makes an
entry in its local copy of the database that the primary is
out_of_service.
• When you shut down the PCS 7 OSx system, each station makes an
entry in its local copy of the database that all other stations except the
primary are out_of_service. The primary role is preserved so that when
you restart OSx, all stations can then contact the primary.
• If a station loses contact with the primary, the system automatically
sets the station to the out_of_service role.
When Role_Change to Normal Executes This command is only
executed when the following conditions are true.
• The local OSx station has an active primary in its database.
• No OSx station in the system is synchronizing to the primary.
When Role_Change to Sys_Admin Executes This command is only
executed when the following conditions are true.
• No OSx station in the system is synchronizing to the primary.
• The selected station is a supervisory station.
When Role_Change to Out_of_Service Executes This command is
executed whenever you select the option.
Automatic Role
Changes