Abstract: A parallel computer system and a block transfer method and computer program for use with the parallel computer system which includes at least one processing unit divided into a plurality of logical processing units and a connecting device which exchanges commands and acknowledgements with the processing unit. The connecting device edits into a single command or acknowledgement individual commands or acknowledgements to be sent to the logical processing units and sends the single command or acknowledgement to the processing unit. The single command or acknowledgement includes a header, a command or acknowledgement code, logical processing unit numbers and pieces of command or acknowledge information corresponding to the logical processing units. The processing unit divides the single command or acknowledge into the individual commands or acknowledgements for the logical processing units and notifies the latter of these commands or acknowledgements.

Abstract: A command is issued from a processing unit to an on-line storage unit and transferred from the on-line storage unit to a back-up storage unit. The received commands are processed in the respective storage units. An overhead of the on-line storage unit is reduced in a hot stand-by system. Storage contents of the on-line storage unit and the back-up storage unit are made coincident in a structure having a plurality of processing units, where the on-line storage unit and the back-up storage unit are connected through a channel device.