Data latency and source historian server failover, Uniint failover – Rockwell Automation FactoryTalk Historian SE 3.0 H2H Interface User Guide User Manual
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FactoryTalk Historian To Historian Interface User Guide
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After the interface is up and running, and if n-way buffering is enabled, the interface will
collect data even if the receiving Historian Server is not available. This means data flow is
not dependent on the receiving Historian Server once the interface has completed is startup
initializations.
Be aware that history recovery can be compromised when the interface is configured for n-
way buffering to a collective. On startup the interface will check the snapshot value on the
receiving Historian Server for each tag in its tag list. The snapshot value is used to determine
the starting point for history recovery. This snapshot check only occurs on the receiving
Historian Server specified in the interface startup file. Therefore if the last value for each tag
assigned to the interface is not the same among Historian Servers in the receiving collective,
it will result in either a data gap or data overlap. The best way to avoid this scenario is to
initialize all Historian Servers in the receiving collective with the same set of data for the
interface tag list prior to implementing the Historian to Historian interface.
Note: The Buffer Subsystem v3.4.375.38 only supports writing to the archive in NO
REPLACE mode. This prevents the Historian to Historian interface from honoring
Location5 archive write options and can lead to data loss. It is recommended users
use a later version of Buffer Subsystem or Historian Bufserv to avoid this issue.
Please check our support website for the latest versions;
Data Latency and Source Historian Server Failover
The source Historian Server (or source Historian Server pair if failover is enabled) should
receive data directly from the interface node populating data for the Historian to Historian
source tag list. Not only will this ensure a seamless data transition on failover, it will also
minimize data latency to the receiving Historian Server(s). In this context data latency is the
time it takes between obtaining a value at the data source and having it arrive at the receiving
Historian Server via the Historian to Historian interface.
UniInt Failover
This interface supports UniInt failover. Refer to the
this document for configuring the interface for failover.