Rockwell Automation FactoryTalk Historian SE 3.0 UniInt Interface User Guide - Manual (Page 79)

UniInt Interface User Manual 73
UniInt Failover Scheme
Introduction
The UniInt failover scheme provides for a hot failover, no data loss solution given a single
point of failover. The scheme requires the data source be able to communicate and service
data to two interfaces simultaneously. Additionally, the failover configuration requires the
interface supports outputs.
UniInt interface level failover may be configured to send data to a H.A. Historian Server
collective. The H.A. Historian Server basically provides redundant Historian Servers to
allow for the un-interuppted collection and presentation of Historian Time series data while a
single Historian Server can be taken down for maintenance or in the case of a hardware error
that causes a single Historian Server to become unavailable. The H.A. Historian Server
collective is described in the Historian Server Reference Guide.
When configured for UniInt failover, the interface routes all data that needs to be sent to
Historian through a state machine. The state machine determines whether to queue the data
or send the data to Historian depending on current state of the interface. When the interface
is in the primary state, any data sent through the interface will be routed to Historian. When
in the backup state, any data sent through the interface will be queued for a short period. The
data being queued by the backup interface ensures a no-data loss failover under normal
circumstances. The same algorithm is used for output data.