Rockwell Automation FactoryTalk Historian SE 3.0 UniInt Interface User Guide - Manual (Page 33)

UniInt Interface User Manual 27
specified if there is only one copy of an interface that is associated with a particular point
source.
2. Set Location4 to correspond to the scan class whose performance is to be monitored. For
example, to monitor scan class 2, set Location4 to 2. See the /f parameter for a
description of scan classes.
3. Set the PointSource attribute to correspond to the /ps parameter on the startup
command-line of the interface.
4. Set the PointType attribute to any of the floating-point point types that are supported by
the Historian Server.
Performance Summaries
UniInt monitors interface performance by keeping track of the number of scans that are hit,
missed, and/or skipped for scan-based input points. Scans that occur on time are considered
hit. If a scan occurs more than 1 second after its scheduled time, the scan is considered
missed. If a scan occurs 1 scan period or more after its scheduled time, then 1 or more scans
are considered skipped. Say that a particular scan class has a period of 2 seconds. If a scan
for this class occurs 1.1 seconds after its scheduled time, then 1 scan has been missed.
However, no scans have been skipped because the next scan still has the opportunity to occur
at its scheduled time, which happens to be 0.9 seconds after the last scan in this case. For
scans that have periods of 1 second or less, the above definition of a missed scan does not
make sense. In these cases, scans are considered either hit or skipped. Since every skipped
scan is also considered to be a missed scan, the scan performance summary should indicate
the same percentage of skipped and missed scans for scan classes with periods of 1 second or
less.
By default, UniInt prints out a performance summary to the message log every 8 hours if the
hit ratio (hit ratio = hits / (hits + misses)) drops below 0.95. The performance summary
shows the percentage of scans that are missed and skipped for every scan class. The
frequency at which performance summaries are printed out can be adjusted using the /perf
command-line parameter.
For interfaces that use unsolicited input points, performance summaries should be inactivated
by setting /perf=0 because performance summaries are meaningless for unsolicited inputs.
UniInt and PI SDK
Prior to the release of the version 1.6.0.2 of the PI API, the PI SDK was required in order to
retrieve long extended descriptors, instrument tags and tag names. The SDK was also
required in order to a use multi-character point source. With the release of the PI API 1.6.0.2,
UniInt based interfaces can support all of these features without using the PI SDK. UniInt
version 4.1 was modified to take advantage of the new API making the use of the PI SDK