System for dynamically changing a system I/O configuration by determining differences between current and future configurations and describing differences to software and hardware control blocks

An installation creates a source I/O definition file (IODF), defining a current system I/O configuration, and a target IODF, defining a future I/O configuration. An activate function is initiated to change the system's hardware and software definition to correspond to the target IODF. A compare function compares the source and target IODFs, and creates a Configuration Change Block (CCB) to efficiently drive the change process. A validation function validates that the proposed change is valid, and the change process updates the hardware and software configuration definitions. If the change process is successful, a notification is sent; if not, a back-out process restores the I/O configuration to its initial state.