Data Request Types

The Config View allows the selection of "Request Types" for archived data.

Note that these options only affect how history data is retrieved from the archive. It cannot influence how data has been or will be added to the archive. Some PVs update at 10Hz and are archived once a minute. Others might update when changed via an operator screen, and are archived for every change. How a PV updates is determined by the front-end device that provides the PV. How it is archived depends on the archive sampling engine. The Data Browser only displays the live and archived data.

Optimized Request

This is the default. The optimized request type automatically switches between original samples and min/max/average information. Under CSS/Preferences/../Trends/DataBrowser, you can configure the number of "bins" used for data retrieval. Assume we configure 500 "bins", and the graph has a one-day time range. If there are less than 500 samples in the archive, you will get those 500 original samples. If there are more, you will get the average sample combined with the minimum and maximum for each "bin".

When "zooming in", the Data Browser will request samples for the new time range, which might reveal more detail and ultimately switch to "original" samples.

The optimized request type therefore tries to minimize the amount of data that needs to be transferred over the network and handled in the plot, while still providing enough information to see how the PV data behaved.

Raw Request

In rare cases, limitations in the optimized request mechanism need to be overcome by enforcing 'raw' data retrieval. In most cases, however, requesting 'raw' data will not provide any new information but only cause your computer to run out of memory.

If you need the raw data for an extended time range for post-processing, you should use the Export View.