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Large number of Log Data Transfer Missed events being logged.

Issue

A large number of "A Log Data Transfer Has been Missed" events are being reported by the AS.

All events are associated with b3 points that have intrinsic logging configured (where log configuration is part of the point properties configuration) and a StruxureWare Building Operation Extended Trend Log is attached to the point.  

Environment

  • b3
  • Log Data Transfer
  • Extended Trend Logs

Cause

We have seen these events reported when the number of log records configured in the b3 point is not evenly divisible by the Maximum Log Transfer Interval in the Extended Trend Log object.

When the Extended Trend Log retrieves data from the objects intrinsic log in the b3 controller, it grabs this data in batches or portions. 

The size of these portions is defined by the Maximum Transfer Interval in the Extended Trend Log configuration. 

For example, where a b3's intrinsic log is set to 1 hour Log Interval and the Log Records is set to 72 (three days), if its associated Extended Trend Log has a Maximum Transfer Interval of 1 Day, the it will grab the first 24 records during the first pass, the next 24 records during the second pass and the remaining 24 records during the last pass. 

If the number of Log Records defined in the point configured is 80 instead of 72, the same Extended Trend Log will grab the remaining data in a fourth pass. 

However, if the amount of data remaining to be grabbed does not represent a span of time equal to the Maximum Transfer Interval, the Extended Trend Log will not grab a full period of data. 

In some cases when this happens data from this fourth pass can be lost and this will be reported as an "A Log Data Transfer Has been Missed: event.

Example:

Using our example above, and an intrinsic log Record Count of 80, the Extended Trend Log will grab the first 24 records during the first pass, the next 24 records during the second pass, the next 24 records during the third pass.  It will then grab the last eight log records in a fourth and last pass.  It is during the transfer of this last smaller group of data where there may be a failure of the data transfer.

Resolution

The number of Log Records configured in the points intrinsic log times the Log Interval should equal a period of time that is evenly divisible by the Maximum Transfer Interval time period.

For example, if the Extended Trend Log is configured for a Maximum Transfer Interval of 24 hours, and the b3 point is configured for a 15 minute Log Interval, the Log Records can be set to either...

  • Log Records = 96  (4 samples per hour X 24 hours -- a full days worth of data)
  • Log Records = 192 (4 samples per hour X 48 hours -- two full days worth of data)
  • Log Records  = 288 (4 samples per hour X 72 hours -- three full days worth of data) and so forth.
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