Rockwell Automation FactoryTalk Historian SE 3.0 UniInt Interface User Guide - Manual (Page 48)

Interface Health Points
42
General Interface Health Tags
The general interface health tags pertain to the operation of the interface in general. A list of
scan class health tags follows. The scan class health tags require a valid scan class be
configured in Location4 of the Historian tag. The general Interface Health tags do not
consider the Location4 value.
Heartbeat
ExDesc Keyword: [UI_HEARTBEAT]
Update Interval: Once a second or based on scan class as described below.
Description:
The heartbeat tag is the primary tag used to determine if the interface is running. If the value
of the heartbeat tag is updating, then the interface is running but not necessarily connected to
and collecting data from a data source. The default update interval is 1 second if there are no
scan classes defined for the interface. If the interface has defined scan classes, the update
interval will be set to the highest frequency (lowest value) scan rate with the following
limitations. If the scan rate is less than 1 second, the update interval will be set to 1 second. If
the scan rate for the highest frequency scan class is greater than 1 minute, the update interval
will be set to 60 seconds. The value written to the heartbeat tag increments from a value
starting at 1, increments to a value of 15 and then restarts at 1.
The heartbeat tag will stop updating if the interface is shut down or if the interface is in a
deadlock situation.
Note: The Interface Health Heartbeat tag is completely separate from the UniInt
Failover Heartbeat tag. An interface can have both an Interface Health Heartbeat tag
and a UniInt Failover Heartbeat tag loaded simultaneously.
Scan Class Information
ExDesc Keyword: [UI_SCINFO]
Update Interval: Once at interface startup and each performance summary interval.
Description:
The Scan Class Information Tag is a string tag that contains the number of scan classes used
by the interface and their associated scan rates. The Heartbeat scan rate is also included in
the string. The tag is updated once at interface startup and at each performance interval.
As an example, the value for the Scan Class Information tag for an interface with three scan
class of 5 seconds, 10 seconds and 60 seconds will be ―3 | 5 | 5 | 10 | 60‖. The first number is
the number of scan classes and the second number is the Heartbeat update rate. The numbers
that follow the Heartbeat depend on the rate and number of scan classes defined. Each scan
class rate will be written in seconds.