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Synchronization states
Standby state
is a viable replacement for the primary controller, and only that configuration data that is
changed and the control data that changes as a consequence of primary controller
execution is synchronized to the secondary controller.
Standby state
The Standby state of operation improves the software upgrade scenario, (such as On-
Process migration) by providing the user with a convenient means to fallback to a
previous software and database if problems are encountered during migration. Standby
state is achieved either from the 'Sync Maintenance' state, via the 'Enable Standby'
command, or due to On-Process Migration. For example, during a controller on-process
migration the standby state allows a user to test the expected behavior of a configured
control strategy using the newer or upgraded software. If controller operation is not
satisfactory, then the controller could be returned to operation with the current software
by invoking the Go-Back to Idle option.
While in the Standby State, the secondary controller contains a database that was
previously synchronized with the primary controller but the secondary is no longer
receiving synchronization-data updates from the primary controller. Moreover, a
Standby Secondary controller is able to switchover into the primary role with this stale
database, but to ensure operator intervention, the C300 CEE execution state is forced to
Idle. There is no time limit to the time duration of the Standby state, and as a
consequence of the secondary not being synchronized, switchover to the secondary may
cause a bump in outputs.
192
Figure 10 C300 Controller synchronization states
Experion C300 Controller User's Guide
Honeywell
R301.1
11/06
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