Rockwell Automation FactoryTalk Historian SE 3.0 UniInt Interface User Guide - Manual (Page 88)

UniInt Failover Scheme
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interface is in a good status as determined by the backup. If the backup interface transitions
to the primary, it will have data in its queue to send to Historian. This queued data is sent to
Historian using the same function calls that would have been used had the interface been in a
primary state when the function call was received from UniInt. If UniInt receives data
without a timestamp, the primary copy uses the current Historian Time to timestamp data
sent to Historian. Likewise, the backup copy timestamps data it receives without a timestamp
with the current Historian Time before queuing its data. This preserves the accuracy of the
timestamps.
Glossary
The following is a list of the terms used by this manual when discussing UniInt Failover.
Active ID Point
The active ID point is located on the data source and identifies which copy of the interface
is primary. The primary interface active ID value is set by the /UFO_ID=n
startup
command-line parameter for the primary interface copy. The value of n must be a positive,
non-zero integer. The value of the active ID point is referred to as the ActiveID.
Backup Interface
The backup interface is used to describe the interface copy which is not the primary
interface.
Cold Failover
In a cold failover configuration, the backup interface is not able to load the list of Historian
tags, but is able to monitor the status of the primary interface. When the primary interface
stops collecting data for any reason, the backup interface will load the list of Historian tags,
start collecting data, and send its data to Historian. This configuration will result in a loss of
data for the time it takes for the backup interface to load the tag list.
Data Source
The term data source is used as the generic term. The data source refers to the
software/hardware where data originates that is to be written to Historian. The data source is
also the destination of data output from Historian. Some examples of data sources are DCSs,
PLCs, software systems using APIs, OPC servers, etc.