An input/output subsystem is configured as a plurality of input/output subsystem images, each of which appears to a program as an independent input/output subsystem. In response to an operating system image submitting an input/output (I/O) request requesting access to an input/output subsystem image, a determination is made as to whether the operating system image is authorized to access the input/output subsystem image. In response to the access being authorized, the I/O request is authorized.