Patent US974929A successfully refreshed from Google Patents.
EP0336549A2
Expired / Lapsed
EP
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Database recovery in a computer system after a system crash
Assignee: International Business Machines Corp
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Filing: 1989-02-24
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Granted: —
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Expires: 2009-02-24
Abstract
Abstract Functions MINBUFLSN and LOWTRANLSN, implemented in a computerized routine, are defined and comprise first and second components of a checkpoint. MINBUFLSN is functionally related to a first update to a first of "dirty" data pages in the RAM buffer. LOWTRANLSN is functionally related to the earliest update of a sequence in a transaction table wherein each update corresponds to an uncommitted transaction. The two components are derived during write-ahead logging and stored in the log header periodically as a function of logging activity. Upon recovery, the checkpoint is retrieved and a functional comparison between the components thereof employed in the recovery algorithm. The conventional analysis pass of the recovery log is avoided and a reduced overhead during logging is provided as well as an efficient recovery.
Inventors
- 👤 William Walter Myre, Jr.
- 👤 Cheng-Fong Shih
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 22:02
CPC Classifications
G; G06; G06F; G06F11/00; G06F11/07; G06F11/14; G06F11/1471; G06F2201/00; G06F2201/80; Y; Y10; Y10S; Y10S707/00; Y10S707/99951; Y10S707/99952; Y10S707/99953
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
106 words
A method of operating a computer system for recovery of a database within the system after a system crash comprising the steps of: storing data corresponding to a plurality of updated data pages; deriving from said data first indicators functionally related to time of update of a corresponding one of said updated pages; storing log records each corresponding to an in-flight database transaction; deriving from said stored log records second indicators functionally related to the time of one of said in-flight transactions; deriving checkpoints as a function of said first and said second indicators; storing said checkpoints; and recovering said database in response to said checkpoint.
Claim 2
Independent Claim
106 words
A method of operating a computer system for recovery of a database within the system after a system crash comprising the steps of: storing data corresponding to a plurality of updated data pages; deriving from said data first indicators functionally related to time of update of a corresponding one of said updated pages; storing log records each corresponding to an in-flight database transaction; deriving from said stored log records second indicators functionally related to the time of one of said in-flight transactions; deriving checkpoints as a function of said first and said second indicators; storing said checkpoints; and recovering said database in response to said checkpoint.
Claim 3
Dependent Claim
44 words
A method according to claim 1 further including the steps of: writing a plurality of log records to a recovery log; generating a measure of said writing of said log records; and writing a plurality of said checkpoints as a function of said measure.
Claim 4
Dependent Claim
28 words
A method according to claim 2 wherein said measure is a number N corresponding to a number of said writes of said log records to said recovery log.
Claim 5
Independent Claim
26 words
A method according to any one of claims 1 to 3 wherein said first indicators are MINBUFLSN's and said second indicators are LOWTRANLSN's as defined herein.
Claim 6
Independent Claim
104 words
A method according to any one of claims 1 to 4 wherein said step of recovering said database comprises the steps of: retrieving said first and said second indicators from one of said stored checkpoints; comparing said first and said second indicators; starting full forward recovery of said database at a location in said recovery log functionally related to said first indicator if said second indicator is equal to or greater than said first indicator; and executing analysis only on log records from said first indicator to a log record preceding said second indicator if said second indicator is less than said first indicator.
Claim 7
Independent Claim
105 words
A method of operating a computer system for generating components of a checkpoint for use in recovery of a database on the system after a system failure, comprising the steps of: generating indicators of a first sequence of occurrence of updates to said database, each said update corresponding to an in-flight transaction and one of said indicators; selecting one of said indicators as a first of said components of said checkpoint; generating indicators of a second sequence of occurrence of first updates to data pages in a buffer; and selecting one of said indicators of said second sequence as a second component of said checkpoint.
Claim 8
Independent Claim
105 words
A method of operating a computer system for generating components of a checkpoint for use in recovery of a database on the system after a system failure, comprising the steps of: generating indicators of a first sequence of occurrence of updates to said database, each said update corresponding to an in-flight transaction and one of said indicators; selecting one of said indicators as a first of said components of said checkpoint; generating indicators of a second sequence of occurrence of first updates to data pages in a buffer; and selecting one of said indicators of said second sequence as a second component of said checkpoint.
Claim 9
Dependent Claim
20 words
A method according to claim 6 wherein said indicators of said first sequence are log sequence numbers as defined herein..
Claim 10
Dependent Claim
23 words
A method according to claim 6 or 7 wherein said first component is a value derived from the function LOWTRANLSN as defined herein.
Claim 11
Independent Claim
31 words
A method according to any one of claims 6 to 8 wherein said one of said indicators of said first sequence corresponds to the earliest said update in said first sequence.
Claim 12
Dependent Claim
13 words
A method according to claim 9 wherein said indicators comprise a transaction table.
Claim 13
Independent Claim
25 words
A method according to any one of claims 6 to 10 wherein said indicators of said second sequence are log sequence numbers as defined herein.
Claim 14
Independent Claim
23 words
A method according to any one of claims 6 to 11 wherein said second component is a value derived from the function MINBUFLSN.
Claim 15
Independent Claim
39 words
A method according to any one of claims 6 to 12 wherein said one of said indicators of said second sequence corresponds to a first update to a first of said data pages in said buffer to be updated.
Claim 16
Independent Claim
25 words
A method according to any one of claims 6 to 13 further comprising the step of storing a representation of said first and second components.
Claim 17
Dependent Claim
16 words
A method according to claim 14 wherein said storing comprises a write to a recovery log.
Claim 18
Dependent Claim
75 words
A computer system for recovery of a database after a system failure comprising means for deriving a plurality of values for MINBUFLSN and LOWTRANLSN (as defined herein), means for storing said derived values of MINBUFLSN, LOWTRANLSN, an updated log sequence number (as defined herein) corresponding to a last written log record, and said database; and means for recovering said stored database as a function of said MINBUFLSN, said LOWTRANLSN, and said updated log sequence number.
Claim 19
Dependent Claim
75 words
A computer system for recovery of a database after a system failure comprising means for deriving a plurality of values for MINBUFLSN and LOWTRANLSN (as defined herein), means for storing said derived values of MINBUFLSN, LOWTRANLSN, an updated log sequence number (as defined herein) corresponding to a last written log record, and said database; and means for recovering said stored database as a function of said MINBUFLSN, said LOWTRANLSN, and said updated log sequence number.
References Cited (Backward Citations)
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