Abstract: In a computer system having a central processing unit, a main storage and at least one I/O device, a plurality of operating systems (OS) can simultaneously run under the control of a control program. For executing an I/O instruction using a central processing unit, a plurality of resident areas of said main storage which do not overlap one another are assigned, under the control of the control program, to the plurality of OSs as main memories therefore, respectively. In responding to an I/O instruction issued by a running one of said plural OSs, an address of said main memory assigned to said running OS which participates in an I/Oo operation requested by said I/O instruction is determined without intervention of the control program, and the address is translated into an address of the main storage of the computer system without intervention of said control program. The I/O operation is then executed by using the address resulting from said address translation.

Abstract: In a virtual machine system (VMS) capable of concurrently running at least one operating system (OS) under one real computer system and a control program (VMCP) for controlling the VMS, the object is to reduce the overhead produced for simulating VM I/Os by direct I/O execution. A VM information area of a real sub-channel control block has a status field in which a flag indicating that the sub-channel is dedicated or not is contained. When the flag is "1", it means that the sub-channel is dedicated to the VM and the sub-channel scheduling by the VMCP is not necessary. As a real interruption priority order is dedicated to a VM, only I/O interruption requests of the VM are queued into the real interruption request queue of that dedicated priority order, and the mixing of VMs in that real interruption priority order is avoided.

Abstract: A file control system for virtual machines capable of executing simultaneously a plurality of operating systems in a single computer system under control of a virtual machine monitor for controlling the operating systems, wherein interface means for file input/output operation are provided between the virtual machine monitor and the operating systems for allowing the virtual machine monitor to manage a plurality of files owned by the virtual machines.

Abstract: In a virtual machine system (VMS) capable of concurrently running at least one operating system (OS) under one real computer system and a control program (VMCP) for controlling the VMS, the object is to reduce the overhead produced for simulating VM I/Os by direct I/O execution. A VM information area of a real sub-channel control block has a status field in which a flag indicating that the sub-channel is dedicated or not is contained. When the flag is "0", it means that the sub-channel is dedicated to the VM and the sub-channel scheduling by the VMCP is not necessary. As a real interruption priority order is dedicated to a VM, only I/O interruption requests of the VM are queued into the real interruption request queue of that dedicated priority order, and the mixing of VMs in that real interruption priority order is avoided.