symbology - How to scale SVG symbol based on zoom level in QGIS?

I am wondering if there is a way to scale SVG files I have stored as blob in a Spatialite database according to the current zoom level in QGIS. My hope is to have the SVG icon resize itself when the map is zoomed in/out. I understand there is a size option in the data defined option, but it does not seem to provide a dynamic sizing option. I am open to options.

Answer

If you have an SVG Marker symbol layer, you can set the size units to map units. That way the icon will always have the same real-world size.

Note that the size in the data-defined properties is not radius or diameter but area - which I find weird and might be considered a bug.