US5043866A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Soft checkpointing system using log sequence numbers derived from stored data pages and log records for database recovery
Assignee: International Business Machines Corp
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Filing: 1988-04-08
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Granted: 1991-08-27
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Expires: 2008-04-08
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 W. Myre, Jr.
- 👤 Cheng-Fong Shih
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 14:52
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: 7
Claim 1
Independent Claim
205 words
A method for use in a computerized database system having a processor and associated memory in a database comprising: storing data corresponding to a plurality of updated data pages in said memory; deriving from said stored data MINBUFLSNs functionally related to updates of corresponding ones of said updated pages; storing log records each corresponding to an in-flight database transaction in said memory; deriving from said stored log records LOWTRANLSNs functionally related to one of said in-flight transactions; deriving checkpoints as a function of said MINBUFLSNs and said LOWTRANLSNs; storing said checkpoints in said memory; writing a plurality of log records to a recovery log in said memory; generating a metric of said writing of said log records comprised of a number N corresponding to a number of said writes of said log records to said recovery log; writing a plurality of checkpoints as a function of said metric; retrieving said MINBUFLSNs and said LOWTRANLSNs from one of said stored checkpoints stored in said memory; comparing said retrieved MINBUFLSNs and said LOWTRANLSNs; and starting full forward recovery of said database by said system at a location in said recovery log functionally related to said MINBUFLSNs if said LOWTRANLSNs is equal to or greater than said MINBUFLSNs.
Claim 2
Independent Claim
205 words
A method for use in a computerized database system having a processor and associated memory in a database comprising: storing data corresponding to a plurality of updated data pages in said memory; deriving from said stored data MINBUFLSNs functionally related to updates of corresponding ones of said updated pages; storing log records each corresponding to an in-flight database transaction in said memory; deriving from said stored log records LOWTRANLSNs functionally related to one of said in-flight transactions; deriving checkpoints as a function of said MINBUFLSNs and said LOWTRANLSNs; storing said checkpoints in said memory; writing a plurality of log records to a recovery log in said memory; generating a metric of said writing of said log records comprised of a number N corresponding to a number of said writes of said log records to said recovery log; writing a plurality of checkpoints as a function of said metric; retrieving said MINBUFLSNs and said LOWTRANLSNs from one of said stored checkpoints stored in said memory; comparing said retrieved MINBUFLSNs and said LOWTRANLSNs; and starting full forward recovery of said database by said system at a location in said recovery log functionally related to said MINBUFLSNs if said LOWTRANLSNs is equal to or greater than said MINBUFLSNs.
Claim 3
Independent Claim
143 words
A method for generating components of a checkpoint for use in recovery of a database, comprising: 1. 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; 2. selecting one of said indicators as a first of said components of said checkpoint; 3. generating LSNs which are indicators of a second sequence of occurrence of first updates to data pages in a buffer; 4. selecting one of said LSNs as a value derived from a function MINBUFLSN corresponding to a first update of a first of said data pages in said buffer to be updated as a second of said components of said checkpoint; 5. writing to a recovery log a representation of said first and second components; 6. generating a measure of log record creation; and
Claim 4
Independent Claim
143 words
A method for generating components of a checkpoint for use in recovery of a database, comprising: 1. 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; 2. selecting one of said indicators as a first of said components of said checkpoint; 3. generating LSNs which are indicators of a second sequence of occurrence of first updates to data pages in a buffer; 4. selecting one of said LSNs as a value derived from a function MINBUFLSN corresponding to a first update of a first of said data pages in said buffer to be updated as a second of said components of said checkpoint; 5. writing to a recovery log a representation of said first and second components; 6. generating a measure of log record creation; and
Claim 5
Dependent Claim
23 words
regulating time between said writing of adjacent ones of said next sets of first and second components as a function of said measurement.
Claim 6
Dependent Claim
23 words
regulating time between said writing of adjacent ones of said next sets of first and second components as a function of said measurement.
Claim 7
Dependent Claim
15 words
The method of claim 2 wherein said measurement comprises N writes to said recovery log.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-08-26 | 1995-02-25 | 1995-08-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-08-26 | 1999-02-25 | 1999-08-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-08-26 | 2003-02-25 | 2003-08-27 | $7700.00 | Window Closed / Lapsed |