ndriver-NPollScheduler
Properties of the Poll Service component for typical field bus drivers include four writable properties and various read-only statistics properties. These properties appear in various Property Sheets under a driver’s network component.
You access this Property Sheet by expanding followed by double-clicking or right-clicking the net network node, clicking and expanding the Poll Service or Poll Scheduler.
The table documents the standard Poll Service properties each driver supports.
| Property | Value | Description |
|---|---|---|
| Poll Enabled | true (default) or false | Enables (true) and disables (false) polling. In history views: true enables a system user to use the Live Updates (play) button in History views to poll for live data for the associated imported history(ies). false renders this button unavailable in history views for the associated imported history(ies). In networks: true polls all associated proxy points and devices that can be polled under the network component or, for a BacnetPoll, under that BacnetStack, Network, and Port. false suspends polling and further value updates from polling do not occur. Note: Poll Service actions Enable and Disable allow access to this property. |
| Fast Rate | hours minutes seconds (defaults to 1 second) | Sets the target polling interval
for devices that can be polled (they are pollable) and assigned to
the Fast Rate group. |
| Normal Rate | hours minutes seconds (defaults to 5 seconds) | Sets the target polling interval
for devices that can be polled (they are pollable) and assigned to
the Fast Rate group. |
| Slow Rate | hours minutes seconds (defaults to 30 seconds) | Sets the target polling interval
for devices that can be polled (they are pollable) and assigned to
the Fast Rate group. |
| Statistics Start | read-only timestamp | Reports either the last
manual reset of poll statistics or, if statistics have not been reset,
the first steady state time immediately following the last station
restart. |
| Average Poll | read-only | Reports the average time spent
during each poll event. This does not relate to the total time required
to complete a poll cycle for any of the three rates. It is the time
spent polling a given group of objects before pausing and switching
to another group either using the same or a different poll rate. |
| Busy Time | read-only | Displays a percentage of time
spent by the poll thread actually polling points using all poll rates.
Includes (in parentheses) the ratio of time spent polling/total time
since statistics were restarted. Given a small amount of time is spent transitioning among poll rates, and with the thread sleeping to evenly space out polling messages, it is unlikely to ever see Busy Time reach exactly 100%. However, any percentage above 95% indicates that the poll thread is basically spending all of its time actually polling. Note: In the case of the Poll Service
for a BACnet network port, because two threads are used for polling,
it is possible to see a Busy Time approaching
200%. In this case, divide Busy Time in half
to get an average busy time for each thread. |
| Total Polls | read only | Reports the total number of
polls conducted and the time spent waiting for polls to execute. This
time is the same time indicated in the ratio of the Busy
Time property. Typically, the total poll count indicates
the number of times the PollService polled any object. It is not a
running total of the actual poll cycles. |
| Dibs Polls | read-only | Reports the percentage and ratio
of the number of DIBS polls versus total polls. |
| Fast Polls | read-only | Reports the number of polls
made processing the fast queue. |
| Normal Polls | read-only | Reports the number of polls
made processing the normal queue. |
| Slow Polls | read-only | Reports the number of polls
made processing the slow queue. |
| Dibs Count | read-only | Reports the current and average
number of components in the DIBS stack. (DIBS stands for Distributed
Internet Backup System). |
| Fast Count | read-only | Reports the current and average
number of components in the fast queue. |
| Normal Count | read-only | Reports the current and average
number of components in the normal queue. |
| Slow Count | read-only | Reports the current and average
number of components in the slow queue. |
| Fast Cycle Time | read-only | Reports the average cycle
time for the fast queue. |
| Normal Cycle Time | read-only | Reports the average cycle
time for the normal queue. |
| Slow Cycle Time | read-only | Reports the average cycle
time for the slow queue. |
Example: Total Polls
You have two points assigned to a fast policy of 1 second, two points assigned to a normal policy of 5 seconds, and two points assigned to a slow policy of 10 seconds. When the statistics update every 10 seconds, you would expect the total polls to increment by 26, where:
Total polls = (2 fast/1 sec * 10 sec) + (2 normal/5sec * 10 sec) + (2 slow/10 sec * 10 sec)
Total polls = 20 fast + 4 normal + 2 slow
Total polls = 26
In some cases, such as a BacnetNetwork, Total Polls may indicate the number of poll messages sent to devices. Potentially, there could be multiple points being processed in a single message, such as if performing “read property multiple” for BACnet devices, or possibly when performing COV subscriptions.
Depending on the driver, additional statistics properties may be present in a poll component. For example, a BacnetPoll has additional properties Device Count, Point Count, and Object Count. See the specific driver guide for unique Poll Service features and information.