Method and apparatus for detecting and recovering from data corruption of a database via read logging
First Claim
1. A method of detecting and recovering from data corruption of a database comprising the steps of logging information about reads of a database to automatically detect and recover from physical corruption of the data in the database using a codeword matching audit algorithm said information about reads comprises one of a start and an end point and length of data read for detection of said physical corruption arising from bad writes of data to the database or corruption arising indirectly therefrom, and maintaining a corrupt transaction table and a corrupt data table for a recovery algorithm.
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Abstract
A method of detecting and recovering from data corruption of a database is characterized by the step of logging information about reads of a database in memory to detect errors in data of the database, wherein said errors in data of said database arise from one of bad writes of data to the database, of erroneous input of data to the database by users and of logical errors in code of a transaction. The read logging method may be implemented in a plurality of database recovery models including a cache-recovery model, a prior state model a redo-transaction model and a delete transaction model. In the delete transaction model, it is assumed that logical information is not available to allow a redo of transactions after a possible error and the effects of transactions that read corrupted data are deleted from history and any data written by a transaction reading Ararat data is treated as corrupted.
120 Citations
60 Claims
- 1. A method of detecting and recovering from data corruption of a database comprising the steps of logging information about reads of a database to automatically detect and recover from physical corruption of the data in the database using a codeword matching audit algorithm said information about reads comprises one of a start and an end point and length of data read for detection of said physical corruption arising from bad writes of data to the database or corruption arising indirectly therefrom, and maintaining a corrupt transaction table and a corrupt data table for a recovery algorithm.
- 43. A method of detecting and recovering from data corruption of a database comprising the steps of logging information about reads of a database to automatically detect and recover from logical corruption of the data in the database using a codeword matching audit algorithm for detection of said logical corruption, maintaining a logical redo log and storing user inputs for a transaction in said logical redo log, and maintaining a corrupt transaction table and a corrupt data table for a recovery algorithm.
- 49. A method of detecting and recovering from data corruption of a database comprising the steps of logging information about reads of a database to automatically detect and recover from logical corruption of the data in the database using a codeword matching audit algorithm for detection of said logical corruption, maintaining a corrupt transaction table and a corrupt data table for a recovery algorithm and deleting the effects of transactions from an image of the database.
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58. A method of detecting and recovering from data corruption of a database comprising the steps of logging information about reads of a database to automatically detect and recover from logical corruption of the data in the database using a codeword matching audit algorithm for detection of said logical corruption and logging the codeword of a logical state found.
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59. A method of detecting and recovering from data corruption of a database comprising the steps of:
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(a) logging information about reads of a database to automatically detect and recover from physical corruption of the data in the database using a codeword matching audit algorithm for detection of said physical corruption, said physical corruption arising from bad writes of data to the database or corruption arising indirectly therefrom;
(b) storing a codeword corresponding to a value of a data item in a record of said combined log of reads and writes; and
(c) performing a forward scan of a log of read and write operations wherein said forward scan adds an identity of data to a corrupt data table whenever said data has failed an audit.
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60. A method of detecting and recovering from data corruption of a database comprising the steps of:
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(a) logging information about reads of a database to automatically detect and recover from logical corruption of the data in the database using a codeword matching audit algorithm for detection of said logical corruption and deleting the effects of transactions from an image of the database;
(b) logging lock information in a logical redo log;
(c) recovering from data corruption using first and second phases, a first redo phase followed by an undo phase;
(d) said redo phase comprising a forward scan of a log of read and write operations; and
(e) said forward scan adding an identity of data to a corrupt data table whenever said data is written by a corrupt transaction wherein said forward scan adds transactions to a corrupt transaction table whenever data is read that is identified in the corrupt data table.
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Specification