INPUT/OUTPUT CONTROL SYSTEM WITH PLURALITY OF CHANNEL PASSESWITH REFERENCE TO INPUT/OUTPUT DEVICE

PURPOSE: To improve a channel path selecting technique by applying an IOP(I/O processor) with an improved capability of testing the using/empty situation of a channel path for an I/O device. CONSTITUTION: A data processing system is constituted of more than one host processors for operating a mutual action through plural channels with plural I/O devices under the control of more than one IOP(I/O processor), and a host memory. A one deep queue for receiving the instruction of the I/O work when each channel is already being used for executing the previously received work is applied to each channel. When the I/O device can perform access through the plural channels to the host computer, the IOP is allowed to judge the using situation/empty situation of each channel and the full/empty situations of the one deep queue of the channel so that an improved channel path selecting capability can be applied to the IOP. Thus, the capability of each IOP can be improved, and the most satisfactory IOP is selected for starting the work in the channel or for judging the next path selection.