Data collection by exception

When a collect record is configured to collect data by exception, data is only collected when there is a significant change.

To collect data by exception, set the Collection Type field in the Collect Row Edit dialog box to exception. Data is only collected if any of the following is true:

• The value increases or decreases by an amount greater than or equal to the value in the Deadband field.

• The Stale data quality attribute changes (flag.fresh).

• The Alarm data quality attribute changes (flag.alarm).

• The Manual data quality attribute changes (flag.manl).

• The Error data quality attribute changes (flag.error).

• The TestMode data quality attribute changes  (flag.testmode).

Collecting data on an exception basis usually requires less disk space. Collecting data by exception from the RealTime database (RTDB) into the Historical database (HDB) is similar to, but independent of, reporting data by exception from remotes into RealTime.

Note: Regardless of whether data from a point is set to be collected periodically or by exception, data is collected from the point at least once an hour, at the start of the hour.