Method for bumpless changeover from active units to back-up units in computer equipment and a device for carrying out the method

摘要

Method for bumpless changeover from active units to backup units in computer equipment and a computer equipment for carrying out the method. The central unit of a computer equipment has an active processor and an active memory as well as redundant units as backup units for the processor and/or the memory. Further, there are members for changeover from an active unit to a corresponding backup unit in the event of a fault in the active unit. The central unit has interrupt routines and carries out write and read operations against the peripheral units of the equipment. A bumpless changeover from an active unit to a backup unit is obtained by establishing rollback points (P₀-P₄) in the program execution by storing the processor state and the memory content in at least all hardware initiated interrupt routines. All operations against the peripheral units are logged after each rollback point. At a changeover (at P₁) to a backup unit, the program execution is returned to the last established rollback point (P₁). Thereafter the execution of the program is resumed without performing any operations against the peripheral units, whereby instead the result of read operations is fetched from log buffers while write operations are skipped, until all the logged operations have been repeated. Thereafter the execution is continued with performing operations against the peripheral units.