Independent channel coupled to be shared by multiple physical processing nodes with each node characterized as having its own memory, CPU and operating system image

A computer system and processing method are provided for coupling multiple physical processing nodes together, wherein each physical processing node is characterized as having its own memory, by either at least one channel which is independent of and coupled to the multiple physical processing nodes or by at least one input/output (I/O) processor, again which is independent of and coupled to the multiple physical processing nodes. The at least one channel and/or the at least one I/O processor couple the multiple physical processing nodes to at least one shared input/output device. Sharing of the at least one channel and/or at least one I/O processor is practical by providing "indirect logical addressing" using logical address tables within the channel subsystem. The logical address tables associate an image identifier (Image-ID) and processing node identifier (PN-ID) concatenation with an indexed logical address for use in communicating I/O operation parameters across the at least one channel.