Virtual machine file control system which translates block numbers into virtual addresses then into real addresses for accessing main storage

Claim 1

In a computer which realizes virtual machines by concurrently running operating system (OS) programs under control of a virtual machine control program, a file access method for enabling an access to a temporary file in terms of a file name assigned to the file and a data block number assigned to a data block to be accessed within the file, wherein the temporary file is a file located in a main storage of the computer, the method comprising the steps of: (a) determining, by one of the OS programs, a device address of a virtual secondary storage device for a temporary file in response to a file access request which designates a file name of the file, wherein the virtual secondary storage device has the same number of virtual areas as a total number of data blocks included in the file; (b) informing, by the one OS program, said virtual machine control program of the device address and a block number within the file designated by the file access request and assigned to a data block to be accessed; (c) translating, under control of the virtual machine control program, the informed block number within the file into a real address for a real data area of said main storage, in which real data area the data block is, or is to be held, the step of translation including: (c1) a first substep of translating the informed block number within the file into a virtual address for a virtual data area assigned to a data block of the informed block number among virtual data areas provided in a virtual secondary storage device assigned with the informed device address, and (c2) a second substep of translating the virtual address into the real address; and (d) accessing said real data area of said main storage under control of the virtual machine control program and in response to the real address obtained by the step (c).