Server Preferences - Charts

Acquire™ takes regular samples of data from the flowcomputers so charts can be drawn. By collecting the data every few seconds for each chart, the database will quickly become very large so it is important to carefully manage the number of data points collected.

For instance if a data point is collected every 15 seconds it will produce 4 * 60 * 24 = 5760. Collecting 100 such point will generate 576,000 points in a day and over a million points in two days. Clearly decreasing the collection period or increasing the number of points drastically increases the number of points collected overall.

Acquire employs techniques to keep the number of data points down to a minimum, for instance when plotting a keypad value it will only plot two points for the start and end points and then draws a straight line in between.

This number of chart points must be managed to stop it getting too large otherwise the performance of the entire database will be affected.

The following settings are available in the Charts tab:

Field	Description
Chart Data Collection Enabled	Allows the collection of chart data to be suspended.
Days to keep Chart Data	The number of days to keep chart data has a big affect on the number of data points collected. The default value is 2 days. If you want to increase the number of days, think about the number of points that you are collecting or increase the chart sample time. Data that is older than the number of days will automatically be removed from the database. This data is purged regularly to stop it from building up. It is actually based on the number of seconds from the current time a setting of 2 days keeps the chart data for the last 172,800 seconds.
Sample Period	The sample period is the amount of time between collecting data from the flowcomputer in seconds. It is not recommended that the sample period be set less than 15 seconds. Note: If too many data points are being collected this can affect the modbus data response rates, especially if the sample period is too quick for the flowcomputer.
Chart Data Cache Size	The size of the chart data records can affect the performance of Acquire™. To ensure that the database runs at maximum performance Acquire™ keeps the most recent chart data in a cache. The size of the cache will depend on the amount of memory installed on the server.