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Parallel data base record distribution method and parallel data base management system

  • US 5,987,462 A
  • Filed: 04/25/1997
  • Issued: 11/16/1999
  • Est. Priority Date: 04/26/1996
  • Status: Expired due to Term
First Claim
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1. A method of dividing a database in parallel in a parallel database management system, wherein the database management system comprises:

  • a plurality of database units each having an external memory unit for storing a division of a database, anda control CPU including means for registering, referencing and altering database configuration information including a number of divisions of the database among said external memory units, means for storing a record in any one of said external memory units, and means for searching and updating the record stored in any one of said external memory units, the database records being distributed among the external memory units associated with each database unit, the stored records being searched and updated in each database unit, thereby achieving a high processing speed;

    said method of dividing a database in parallel, comprises the steps of, by said control CPU;

    referencing said database configuration information;

    calculating the value of a predetermined portion of the data of a record by a hash function;

    uniquely determining an external memory unit to store said record to thereby realize the divided storage of the record when storing or adding said record;

    searching and updating the external memory units associated with all the database units included in the database to thereby realize the desired record search without using the hash function when searching and updating a record;

    said method further comprising the steps of;

    storing in memory means an average record increment rate per unit time for the whole database and the number of records in each of said external memory units;

    temporarily altering the hash function used for storing the records during a predetermined time proportional to the total number of records in said external memory units before addition divided by the average record increment rate per unit time for all of said external memory units when increasing the number of divisions of the database due to the addition of a database unit; and

    selecting the added external memory unit in priority over the other external memory units as an external memory unit assigned for storage as a result of the calculation result using the hash function.

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