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Browse Prior Art Database

Tracking Register

IP.com Disclosure Number: IPCOM000043046D
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Sutton, AJ: AUTHOR

Abstract

This procedure is used to verify if storage backed-up data is valid by retaining a validity indicator outside of storage. Present design for warmstart recovery is to retain back-up data of storage in a file medium for components that are required to recover if an error occurs. The back-up copy is good if the main storage copy has not been altered between the intervals when the back-up copy is taken. If altered, a change bit is kept in storage. Upon detection of an error, the contents of main storage which contain the change bits are dumped into the file. A fresh copy of the control program is loaded, and the dump is examined to see if the change bits were on. If no dump is available, the system cannot recover. In this case where the change bits are off, the back-up copy is good and the system could have recovered.

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Tracking Register

This procedure is used to verify if storage backed-up data is valid by retaining a validity indicator outside of storage. Present design for warmstart recovery is to retain back-up data of storage in a file medium for components that are required to recover if an error occurs. The back-up copy is good if the main storage copy has not been altered between the intervals when the back-up copy is taken. If altered, a change bit is kept in storage. Upon detection of an error, the contents of main storage which contain the change bits are dumped into the file. A fresh copy of the control program is loaded, and the dump is examined to see if the change bits were on. If no dump is available, the system cannot recover. In this case where the change bits are off, the back-up copy is good and the system could have recovered. However, if the change bits were on, the dump copy would have had to been used since the back-up is no longer valid. When the change bits are placed in an independent register outside the elements being recovered, the system may be recovered from a failure either in the engine doing the dump or in storage being dumped because the change bits can be looked at and, if off, the back-up copy used. If the change bits are on, then the system cannot recover. The contents and use of the tracking register(s) can be expanded for use by other components as well, such as for functional recovery routines. As a component progresses through its execu...