OpenVMS: distributed locking (we're barely catching up with it, in 2017!) -- see e.g. http://download.oracle.com/otndocs/products/rdb/pdf/rdbtf05_... , filesystem versioning (we still have nothing like it, and applications like ClearCase (very poorly) try to implement their own over filesystems that don't support it). ASTs (see https://en.wikipedia.org/wiki/Asynchronous_System_Trap ) are also great, but I think something akin to them exists in Windows.