Watchdog point

The watchdog point is a PI point that belongs to the current interface. UniInt 4.3.0.0 and later supports a heartbeat point, which is configured on the Health Points page. Although any point may be used, OSIsoft recommends that you use this heartbeat point as a watchdog point.

• Click the Tag Search button to search for a point that belongs to the current interface as the watchdog point.

• The Tag Search dialog box displayed will be connected to the host PI Server. Search for the interface point that will act as the watchdog point, select it, and click OK.

PI Interface Status monitors a watchdog point to determine the status of the monitored interface. When choosing an interface watchdog point, consider the following:

• The scan rate of the interface watchdog point should reflect the scan rate of the majority of the points in the monitored interface. For example, if the majority of the points in the monitored interface have a scan rate of 10 seconds, the interface watchdog point should have a scan rate of 10 seconds.

• The scan rate of the interface watchdog point should be slightly more frequent than the monitor frequency (Location4) of the PI Interface Status point. For example, if you want PI Interface Status to monitor an interface every 1 minute, its interface watchdog point should be updating around every 30 seconds.

• The monitor frequency of the PI Interface Status point should depend upon the scan rates of the points in the monitored interface. Choose a monitor frequency that is a little less frequent than the majority of the scan rates for the points in the monitored interface.

• For example, an interface with most of its points scanning every 30 seconds could have a monitor frequency of 1 minute. An interface with most of its points scanning every second could have a monitor frequency of 10 seconds.

In addition to the scan frequency, the Location2 and Location3 attributes must also be set.

• Scan Frequency

  The scan frequencies listed are the scan frequencies currently defined for the PI Interface Status Utility (PIIntStatus) service. Select the appropriate scan frequency for the point selected. If a different scan frequency is required, the PIIntStatus configuration needs to be modified and a new scan class needs to be added before proceeding. Scan classes are configured on the General page of PI ICU.

• Location2

  Location2 defines ISU behavior when data becomes stale. This parameter has three possible values:

  • 0

    No digital state written to input points.

  • 1

    Write ISU Saw No Data.

  • 2

    Write ISU Saw No Data, but ignore interface shutdown state.

• Location3

  This selection is only enabled if Location2 is not equal to 0. It defines ISU behavior when communication resumes. This parameter has three possible values:

  • 0

    Remove the system digital state written by ISU.

  • 1

    Do not remove the system digital state written by ISU.

  • 2

    Remove the system digital state written by ISU if an archive value is present.