Rockwell Automation FactoryTalk Historian SE 3.0 UniInt Interface User Guide - Manual (Page 90)

UniInt Failover Scheme
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Input Data
The term input data refers to data that originates on the data source and is collected by the
interface and then written to the Historian Server.
Interface Control Points
An interface control point is a point on the data source that is used by UniInt to negotiate
interface failover. The interface must be able to read the value of this point from the data
source and write a value to this point on the data source. There are two types of interface
control points: heartbeat points and active ID points. The value of these control points are
echoed back to the Historian Server.
Interface Control Tags
The failover solution requires six interface control tags (Historian tags). When UniInt starts
and loads the list of Historian tags, it will retrieve the information needed to be able to read
from and write to the interface control points. If any of the six interface control tags are not
found or fail to be loaded by the interface, the interface will log a message stating that the
interface is not properly configured to participate in failover and then shutdown.
Interface Copy
The term interface copy refers to a single interface executable that is participating in a
failover configuration.
Interface Instance
An interface instance is defined as an interface with a unique set of Historian tags
determined by PointSource and interface ID (/id startup parameter). An interface instance
may be redundant or standalone. When discussing a failover configuration, the interface
instance includes both redundant copies of the interface since they have the same
PointSource and interface ID.
Output Data
The term output data refers to data that originates in Historian or the failover copy of the
interface itself, and written to the data source.