Rockwell Automation FactoryTalk Historian SE 3.0 UniInt Interface User Guide - Manual (Page 14)

Interface Startup Parameters
8
Parameter Description
adhere to a wall clock for this particular scan class. Periods of
2, 3, 4, 6, 8, 12, or 24 hours or periods that are a multiple of
24 hours are implicitly scanned according to wall-clock
scheduling as long as a time offset is explicitly defined for the
scan class.
A scan class can be explicitly defined to adhere to wall-clock
scheduling by appending, L to the scan class definition. For
example,
/f=23:00:00,08:00:00,L will invoke wall-
clock scheduling for the scan class. This means that the
period of the scan class will be 24 hours during daylight
saving time to standard time transitions and 22 hours during
standard time to daylight savings time transitions. Appending,
L has no effect when the period of the scan class is less than
or equal to 1 hour.
Similarly, a scan class can be explicitly defined to ignore wall
clock scheduling by appending
,U to the scan class
definition. For example, /f=24:00:00,08:00:00,U
means that the scan period will always be 24 hours, even
across daylight savings time transitions.
An interesting case occurs with wall-clock scheduling on the
spring forward time change for a scan class defined as
/f=02:00:00,00:30:00. Under normal operation,
scans will occur at 00:00:30, 02:30:00, 04:30:00, and so on.
However, during the spring forward time change, there is no
wall clock time of 02:30:00. In this case, the interface skips
the scan entirely and performs the following scan at 04:30:00.
/foxutc
Optional
If this parameter is specified, UniInt will determine the UTC
time of the Historian Server node in the same manner that the
Foxboro interface determines the UTC time of the Historian
Server node.
This option has been added because there are situations
where the default method of calculating the UTC offset
between the interface node and the Historian Server node
does not work properly. The Foxboro interface on Windows is
one example where the default method does not work
(whether or not the PI SDK is enabled). For Foxboro, the time
zone on the interface node is always set to GMT standard
time, but the wall clock time is still adjusted by 1 hour during
daylight savings time changes. This means that the UTC time
on the interface node jumps by 1 hour over a DST transition.
When the PI SDK is not enabled, another example where the
default method for calculating the UTC offset fails is when the
interface is communicating to a Historian Server across a time
zone that differs by a fraction of an hour. For example, the
default method fails when there is a 30-minute difference in
time zones between the interface node and the Historian
Server node. The 30-minute timezone difference can be
handled by enabling the /foxutc option or the /pisdk=1 option.
This parameter is obsolete if the API version is 1.6.x or higher
and the Historian Server is version 2.x or higher. If the API
functions introduced with version 1.6.1 of the API and 2 of the
Historian Server are supported, UniInt will use the API
function pitm_fastservertimeutc to determine the UTC time of
the Historian Server.