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Soft checkpointing system using log sequence numbers derived from stored data pages and log records for database recovery

  • US 5,043,866 A
  • Filed: 04/08/1988
  • Issued: 08/27/1991
  • Est. Priority Date: 04/08/1988
  • Status: Expired due to Term
First Claim
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1. 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.

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