System for bumpless changeover between active units and backup units by establishing rollback points and logging write and read operations
First Claim
1. In computer equipment, a method of bumpless changeover of function from active units to backup units in a central unit, the central unit having at least one active processor, at least one active memory, at least one redundant unit as a backup unit for at least one of said active units, and members for effecting the changeover of the function from an active unit to a backup unit, the processor handling interrupts with the aid of interrupt routines of which at least some are hardware initiated, each of the interrupt routines having one entry point, where the execution of the routine is started, and one interrupt acknowledgement point, the central unit effecting write and read operations against peripheral units included in the computer equipment, wherein the method comprises the following steps:
- (a) establishing successive rollback points by the active processor during program execution, in at least all hardware initiated interrupt routines between the entry point and the interrupt acknowledgement point, by storing status of the active processor and at least contents of those parts of the active memory which have been modified by the active processor;
(b) logging said write and read operations against the peripheral units after each rollback point;
(c) after changeover of the function from an active unit to a backup unit, returning the program execution to the last established rollback point by restoring the contents of the active memory and the status of the active processor to the respective contents and status established by a corresponding unit previously active at said rollback point, whereafter resuming the program execution without carrying out any write and read operations against the peripheral units;
(d) during the following program execution, fetching the results of the read operations already performed against the peripheral units from the log until all logged operations have been repeated; and
(e) continuing the program execution while carrying out operations against the peripheral units.
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Accused Products
Abstract
The central unit of a computer equipment has a processor and a 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; by logging all operations against the peripheral units after each rollback point; by returning the program execution, after a changeover (at Pf) to a backup unit, to the last established rollback point (P1); and by thereafter resuming the execution without performing any operations against the peripheral units, whereby instead the result of read operations is fetched from the log and write operations are skipped, until all the logged operations have been repeated; and by thereafter continuing the execution while performing operations against the peripheral units.
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Citations
13 Claims
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1. In computer equipment, a method of bumpless changeover of function from active units to backup units in a central unit, the central unit having at least one active processor, at least one active memory, at least one redundant unit as a backup unit for at least one of said active units, and members for effecting the changeover of the function from an active unit to a backup unit, the processor handling interrupts with the aid of interrupt routines of which at least some are hardware initiated, each of the interrupt routines having one entry point, where the execution of the routine is started, and one interrupt acknowledgement point, the central unit effecting write and read operations against peripheral units included in the computer equipment, wherein the method comprises the following steps:
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(a) establishing successive rollback points by the active processor during program execution, in at least all hardware initiated interrupt routines between the entry point and the interrupt acknowledgement point, by storing status of the active processor and at least contents of those parts of the active memory which have been modified by the active processor; (b) logging said write and read operations against the peripheral units after each rollback point; (c) after changeover of the function from an active unit to a backup unit, returning the program execution to the last established rollback point by restoring the contents of the active memory and the status of the active processor to the respective contents and status established by a corresponding unit previously active at said rollback point, whereafter resuming the program execution without carrying out any write and read operations against the peripheral units; (d) during the following program execution, fetching the results of the read operations already performed against the peripheral units from the log until all logged operations have been repeated; and (e) continuing the program execution while carrying out operations against the peripheral units. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a computer equipment having a central unit wherein bumpless changeover of function from active units to backup units take place, the central unit having at least one active processor for handling interrupts with the aid of interrupt routines of which at least some are hardware initiated and have an entry point in which the execution of the routine is started and an interrupt acknowledgement point, the central unit further including at least one active memory, at least one redundant unit as a backup unit for at least one of said active units, and members for effecting changeover of the function from an active unit to a backup unit, the central unit effecting write and read operations against peripheral units included in the computer equipment, wherein the computer equipment further comprises:
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(a) members for establishing successive rollback points for the active processor during program execution by storing, in at least all hardware initiated interrupt routines between the entry point and the interrupt acknowledgement point, status of the active processor and at least contents of those parts of the active memory which have been modified by the active processor; (b) members for logging said write and read operations against the peripheral units after each rollback point; (c) members, connected to said storing members, for returning the program execution to the last established rollback point, after changeover of the function from the active unit to the backup unit, by restoring the contents of the active memory and the status of active processor to the respective contents and status established by a corresponding unit previously active at said rollback point, and thereafter for resuming the program execution without carrying out any write and read operations against the peripheral units; and (d) members, connected to said logging members, for fetching, during the following program execution, results of read operations already performed against the peripheral units from the log until all logged operations have been repeated, and thereafter to continue the program execution while carrying out operations against the peripheral units. - View Dependent Claims (10, 11, 12, 13)
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Specification