Immediate duplication of I/O requests on a record by record basis by a computer operating system

Claim 1

A method performed by a computer operating system for controlling a computer system, said computer system comprising a central processing unit in which said operating system is installed, one or more direct access peripheral devices, at least one device controller connected to and controlling said direct access peripheral devices, said device controller being connected to a channel of said central processing unit and responsive to said operating system, said operating system including a virtual input/output request processor connected to a virtual-to-real channel word mapping module, said mapping module mapping virtual addresses to real addresses of said direct access peripheral devices in response to a request from said virtual input/output request processor, said operating system incorporating an optional user invoked mirror command, said mirror command specifying a virtual address of a primary logical device and a virtual address of a mirror logical device to write data to said virtual addresses, said mirror command optionally being invoked or turned off during a computer session by a user, the method performed by said operating system comprising the steps of: building duplicate request input/output data blocks for said primary logical device and said mirror logical device when said mirror command is invoked; transferring control to said virtual input/output request processor of said operating system, said virtual input/output request processor accessing said virtual-to-real channel word mapping module of said operating system to map the virtual addresses of said primary logical device and said mirror logical device to respective real addresses on one or more of said direct access peripheral devices; said device controller executing a write request from said virtual input/output request processor of said operating system to write said data blocks for said primary logical device and said mirror logical device to said respective real addresses on one or more of said direct access peripheral devices, said data blocks being composed of a plurality of records, said operating system controlling said device controller to write a record from the data block for said primary logical device, then to write a record from the data block for said mirror logical device, until all records from both said data blocks have been written thereby performing a substantially simultaneous write operation for both said data blocks; verifying by said virtual input/output request processor of said operating system that said data blocks have been correctly written to said respective real addresses of said primary logical device and said mirror logical device; and said operating system returning control to said user upon verification that said data blocks have been correctly written to said respective real addresses on said one or more of said direct access peripheral devices.

Claim 2

A method performed by a computer operating system for controlling a computer system, said computer system comprising a central processing unit in which said operating system is installed, one or more direct access peripheral devices, at least one device controller connected to and controlling said direct access peripheral devices, said device controller being connected to a channel of said central processing unit and responsive to said operating system, said operating system including a virtual input/output request processor connected to a virtual-to-real channel word mapping module, said mapping module mapping virtual addresses to real addresses of said direct access peripheral devices in response to a request from said virtual input/output request processor, said operating system incorporating an optional user invoked mirror command, said mirror command specifying a virtual address of a primary logical device and a virtual address of a mirror logical device to write data to said virtual addresses, said mirror command optionally being invoked or turned off during a computer session by a user, the method performed by said operating system comprising the steps of: building duplicate request input/output data blocks for said primary logical device and said mirror logical device when said mirror command is invoked; transferring control to said virtual input/output request processor of said operating system, said virtual input/output request processor accessing said virtual-to-real channel word mapping module of said operating system to map the virtual addresses of said primary logical device and said mirror logical device to respective real addresses on one or more of said direct access peripheral devices; said device controller executing a write request from said virtual input/output request processor of said operating system to write said data blocks for said primary logical device and said mirror logical device to said respective real addresses on one or more of said direct access peripheral devices, said data blocks being composed of a plurality of records, said operating system controlling said device controller to write a record from the data block for said primary logical device, then to write a record from the data block for said mirror logical device, until all records from both said data blocks have been written thereby performing a substantially simultaneous write operation for both said data blocks; verifying by said virtual input/output request processor of said operating system that said data blocks have been correctly written to said respective real addresses of said primary logical device and said mirror logical device; and said operating system returning control to said user upon verification that said data blocks have been correctly written to said respective real addresses on said one or more of said direct access peripheral devices.