An apparatus, program product and method to dynamically control the bindings between Input/Output Adaptors (IOA's) and Input/Output Processors (IOP's) in a hierarchical I/O interface of a computer, such that an IOA can be dynamically reassigned from one IOP to another IOP such that the latter IOP takes over management of data transfer between the processing complex of the computer and the IOA from the former IOP. At least partial system availability is maintained in the computer during dynamic reassignment to minimize system downtime and simplify maintenance operations on the computer.