Evaluate and Control Data Compression

You can achieve optimum performance in Historian by carefully controlling the volume of dynamic data it collects and archives. You need enough information to tell you how the process is running, but you do not need to collect and store redundant or non-varying data values that provide no useful information. More information can be found in the Notes on Collector and Archive Compression reference.

Control Data Flow

You can control the amount of online or dynamic data the system handles at a given time by adjusting certain system parameters. The general principle is to control the flow of data into the archive either by adjusting the rate at which the collectors gather data or by adjusting the degree of filtering (compression) the system applies to the data collected.

This manual describes the detailed procedures for executing these adjustments in the sections: Configuring Archives, Configuring Tags, and Configuring Collectors.

Adjust the following parameters to reduce the rate of data flow into the server.

Reduce the polling rate by increasing the collection interval for unsolicited and polled collection.
Enable collector compression and optionally use compression timeout.
Set the compression deadband on the collectors to a wider value.
Use the collector compression timeout.

Adjust the following parameters to increase the filtering applied by the archiver in the server.

Enable archive (trend) compression.
Set the archive compression deadband to a wider value.
Where possible, use the scaled data type and enable input scaling on selected tags.
Where possible, select milliseconds or microseconds rather than seconds for time resolution. Seconds is optimum for most common devices. This affects disk space.

Evaluate Data Compression Performance

You can determine how effectively data compression is functioning at any given time by examining the system statistics displayed on the System Statistics screen of the Historian Administrator, as shown in the Historian Administrator (System Statistics) Screen.

The compression field at the top of the screen shows the current effect of archive compression. Values for this parameter should typically range from 0 to 9%. If the value is zero, it indicates that compression is either ineffective or turned off. If it shows a value other than zero, it indicates that archive compression is operating and effective. The value itself indicates how well it is functioning. To increase the effect of data compression, increase the value of archive compression deadband so that compression becomes more active.