Rockwell Automation FactoryTalk Historian SE 3.0 H2H Interface User Guide - Manual (Page 24)

Principles of Operation
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Int16/32 Yes Yes No
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Interface Status Events
The FactoryTalk Historian to Historian interface may update a tag to indicate a specific status
event. These status events represent data that is generated by the interface and therefore will
not exist for the source tag.
There are three specific status events generated by the interface:

IO Timeout status events are triggered when the interface loses a Historian Server
connection. This information informs users that current data is not being collected.
An event is written to indicate the time of disconnection and another event is written
to indicate the time of reconnection.

Access Denied status events are written whenever the interface is denied access to a
tag‟s data or attribute information.

Intf Shut status events are enabled through /stopstat startup parameter. When
enabled an event is written when the interface is stopped and again on startup. These
events tell users no data is being collected because the interface is not running. See a
more detailed description in the “Command-line Parameters” section.
To prevent a data mismatch between Historian Servers these status events should be disabled.
If enabled these events create a data gap that will not be filled through history recovery.
Each tag receives an „IO Timeout‟ event at the time of Historian Server disconnection and a
second event at reconnection. Likewise, when the interface is stopped and started a
„Shutdown‟ event is written to each tag. History recovery begins either at the start of the
recovery period or a tag‟s current value, whichever is more recent. The status events are
updated prior to performing history recovery, making them the starting point of the recovery
period for each tag. This results in a gap in data for a time period that might otherwise be
recovered.
Interface status events are configured on a tag-by-tag basis through the Location3 tag
attribute. Interface shutdown events are enabled through the interface startup script. By
default shutdown events are not written by the interface.
Adding, Removing and Editing Tags
Tag definitions can be modified while the interface is running. The interface periodically
checks with the receiving Historian Server for tag configuration updates. These updates
include adding, editing, and removing tags. During normal operation the interface checks for
updates every two minutes. It will only process up to 25 tag updates on any given update.
This is to prevent the processing of tag updates from delaying data collection. If there are
more than 25 tag updates, the interface will check again every 30 seconds until all updates
have been processed. Processing tag updates is a low priority for the interface. If a large