In QGIS I have a polygon SHP layer. The layer contains rings. I am reshaping the polygon layer by cutting away large areas of the polygons. When cutting away a part of the polygon that contains a ring, what happens to the ring? Is it completely removed?
I don't think anything happen to the ring as the Reshape tool does not allow rings to be cut if more than one polygon is crossed. The documentation regarding reshaping features might be helpful in describing this in more detail. The following quote is taken from the link:
You can reshape line and polygon features using the Reshape Features icon on the toolbar. It replaces the line or polygon part from the first to the last intersection with the original line. With polygons, this can sometimes lead to unintended results. It is mainly useful to replace smaller parts of a polygon, not for major overhauls, and the reshape line is not allowed to cross several polygon rings, as this would generate an invalid polygon.
If you want to reshape rings then make sure you only draw a line covering the ring itself. There is also the Delete Ring tool if you want to completely remove them.