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Database management system

  • US 5,668,991 A
  • Filed: 02/09/1995
  • Issued: 09/16/1997
  • Est. Priority Date: 03/31/1994
  • Status: Expired due to Term
First Claim
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1. A database system comprising:

  • (a) a database file comprising a plurality of database records, each record having a database identifier;

    (b) a database dump file comprising a copy of said database file at a particular point in time;

    (c) a journal file and an archived journal file, each comprising a sequence of after-image records, each said after-image record having a database identifier indicating which of said database records that record relates to;

    (d) means for performing a series of updates on said database file and, for each of said updates, writing an after-image record into said journal file;

    (e) means for periodically merging said journal file into said archived journal file and for filtering said archived journal file by sorting the after-image records in said archived journal file into order of their database identifiers and removing all but the latest after-image record relating to each database record; and

    (f) recovery means, operative in the event of a database failure, for applying said archived journal file to said database dump file, to reconstruct said database file.

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