Architectural mode configuration

A determination is made that a configuration architectural mode facility is installed in a computing environment that is configured for a plurality of architectural modes and has a defined power-on sequence that is to power-on the computing environment in one architectural mode of the plurality of architectural modes. Based on determining that the configuration architectural mode facility is installed, the computing environment is reconfigured to restrict use of the one architectural mode. The reconfiguring includes selecting a different power-on sequence to power-on the computing environment in other architectural mode of the plurality of architectural modes, wherein the other architectural mode is different from the one architectural mode, and executing the different power-on sequence to power-on the computing environment in the other architectural mode in place of the one architectural mode restricting use of the one architectural mode.