Ronald Allen Simpson

US Patent:

42053749, May 27, 1980

Filed:

Oct 19, 1978

Appl. No.:

5/953063

Inventors:

Henry Bardsley - Saratoga CA
Fernando A. Luiz - Monte Sereno CA
Nils F. Nilsen - Tucson AZ
Ronald C. Simpson - San Jose CA

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F 1100
G06F 1300

US Classification:

364200

Abstract:

A method and means for the recovery of non-logged data by a CPU/channel from a storage subsystem, which data would normally be overwritten upon the subsystem being RESET by the CPU/channels. A defaulting control unit simultaneously initiates a DISCONNECT IN sequence to its attaching channels and sets an appropriate status bit at a control unit/control unit communications interface. The channel responds to the DISCONNECT IN with a SELECTIVE RESET interface sequence which sequence is buffered by the defaulting control unit. Meanwhile, the companion functioning control unit, when operating at its lowest interrupt level, polls the status bit periodically and offloads data registers through the interface connection from the defaulting unit within a predetermined time. At the end of this interval, the SELECTIVE RESET is honored, thereby erasing all data in the defaulting control unit registers.