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AssigneeInternational Business Machines Corporation
InventorsRobert F. Buxton, Stephen R. Walker, Stephen J. Hobson, Paul Hopewell, Paul Kettley, Robert D. Millar, Peter Siddall
Estimating the term…
The invention relates to the recovery of data in a database of database records, following a failure of a media containing said database. The data recovery uses a backup of the database and a log of log records detailing any changes in the database which are not captured in the backup. The log is replayed starting with the most recent log record. It is the determined for each successive log record, that relates to an operation on a database record, whether processing the log record will result in the most recent state of the corresponding database record, and if so, the log record is processed. Subsequently additional data is restored from the backup.
A method for recovering data in a database of database records, following a failure of a media containing said database, said data recovery using a backup of the database and a log of log records detailing any changes in the database which are not captured in the backup, the method comprising the steps of:
A method for recovering transactional data in a database following a failure of a media containing said database said data recovery using a backup of the database and a log of log records detailing any changes in the database which are not captured in the backup, the method comprising the step of:
An apparatus for recovering data in a database of database records, following a failure of a media containing said database, said data recovery using a backup of the database and a log of log records detailing any changes in the database which are not captured in the backup, the apparatus comprising the steps of:
An apparatus for recovering transactional data in a database following a failure of a media containing said database, said data recovery using a backup of the database and a log of log records detailing any changes in the database which are not captured in the backup, the apparatus comprising:
A system for recovering data in a database of database records, following a failure of a media containing said database, said data recovery using a backup of the database and a log of log records detailing any changes in the database which are not captured in the backup, the system comprising:
A system for recovering transactional data in a database following a failure of a media containing said database, said data recovery using a backup of the database and a log of log records detailing any changes in the database which are not captured in the backup, the system comprising:
Dependencies are inferred from the claim text.
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Error detection or correction of the data by redundancy in operations: in transactions
Management of the backup or restore process: backup restoration techniques
Error detection or correction of the data by redundancy in operations: involving logging of persistent data for recovery
Indexing scheme relating to error detection, to error correction, and to monitoring: database-specific techniques
Term end not estimated
The present invention relates to data processing systems, and more particularly to data recovery following a media failure within such systems
Even the most reliable of data processing systems are susceptible to main storage media failure (e.g. disk) resulting in loss of data from a database stored thereon. Customers rely on the ability to be able to recover such data and systems enable recoverability by periodically backing up the database to a direct access non-volatile storage device (such as a hard disk drive). A sharp copy backup may be taken or alternatively a fuzzy backup. With the sharp copy, system activity is halted whilst the backup is taken and is only restarted once the backup has finished. A log is used to record subsequent operations on the database until the next backup is taken. With a fuzzy backup, the database is copied in parallel with updates by a database engine. For both cases, at recovery time the backup is restored and then the log replayed forwards (starting with the oldest log record) to apply any subsequent changes to the database. A typical computer system 10 is shown in FIG. 1 including a database 20 which is backed up by backup component 30 and logging component 40 to disks 50 and 60.
Following a system failure resulting in the loss of a database's content it is necessary to restore it as quickly as possible from the backup copy and the log. In a volatile database, such as with message queuing, the contents of the database change rapidly so with the traditional approach of restoring the backup and then applying updates from the log in forward time sequence many redundant database updates will be made since each update may be superseded by another update or deletion.
A preferred embodiment of the present invention will now be described, by way of example only, and with reference to the following drawings:
FIG. 1 shows a data recovery system according to the prior art;
FIGS. 2a and 2b show data recovery in a non-transactional environment according to a preferred embodiment of the present invention;
As previously mentioned, in a volatile database, the contents of the database change rapidly so with the traditional approach of restoring the backup and then applying updates from the log in forward time sequence many redundant data base updates will be made since each update may be superseded by another update or deletion.
Thus by replaying the log backwards only the latest version of any record is applied to the database and consequently unnecessary updates are avoided.
A preferred embodiment of the invention will first be described, with reference to FIGS. 2a and 2b, for a non-transactional environment.