The History Recording Properties section of the Mange Points menu allows you to change the way history is stored for each point in the Vantage Point Server.All points have a History Recording Properties section in the Manage Points menu. As such, we explain the configuration of point history here, rather than repeating the same information for each type of device. The History Recording Properties section contains the following properties, which are explained below: Maximum History Entries, Approximation Method, Rollover Value, Recording Interval.
Maximum History Entries
This field allows you to control how many entries are stored in history. You can either set it to auto, or set it to a specific number, which will precisely limit how many entries are kept.
The default (and recommended) value is auto, which provides an optimized balance between memory usage, high detail, and longevity. The auto setting accomplishes this by distributing history unevenly across time. With Maximum History Entries set to auto, the server will keep 2 weeks of hourly recorded data, 6 months of daily recorded data, and 20 years of monthly recorded data. This should cover the most common types of plots and charts that this data lends itself to, and requires just of 500 entries, compared to about 175,000 entries of all hourly data.
In some cases, you may want to change this field to a specific value. This will force the distribution of history to be evenly distributed across time, and it will allow you to get finer resolution in history logging. Since auto does not allow finer than hourly history, you must set Maximum History Entries to a number if you want history every second or minute. Warning: logging too many history entries can cause the server to crash, or perform very poorly.
Approximation Method controls how data from an interval is approximated. You can choose from several options:
Instantaneous Value - stores the end of each recording interval.
Min From Interval - keeps the smallest value polled within the last recording interval.
Max From Interval - keeps the largest value polled with the last recording interval.
Average Over Interval - keeps the average of all values polled over the last recording interval.
Sum With Rollover - this method is provided to correct metered readings with a rollover. It is meant specifically for meters that are known to be 'always increasing'. If this approximation method is chosen, the rollover effect will be corrected, and the value will continue to increase, instead of resetting back to zero.
Rollover Value This parameter is only changeable if the Approximation Method is set to Sum With Rollover. The correct rollover value must be specified for Sum With Rollover to work correctly.
Recording Interval This value specifies how frequently history should be recorded. You can select what time unit to specify the interval in, and provide any positive number to specify how long the interval will be. Note that the Recording Interval has no effect on how frequently the point is updated (to change the update frequency, you must change the Device Polling Rate)
