Method of determining and storing indexing data on a sequential data storage medium for supporting random access of data files stored on the medium

  • US 6,349,294 B1
  • Filed: 03/15/1999
  • Issued: 02/19/2002
  • Est. Priority Date: 07/31/1998
  • Status: Expired due to Term
First Claim
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1. A method of retrievably storing indexed data on a sequential data storage medium, the data indexed according to a predetermined order, comprising the steps of:

  • storing a data file on the sequential storage medium;

    identifying the presence of a last written index portion including reference to locations of other previous index portions comprising portions of an index range according to the predetermined order, wherein an index portion includes up to a predetermined plurality of entries within the portion of the index range;

    determining an index position for index data relating to the data file within the identified last written index portion according to the predetermined order;

    for any of the identified previous index portions, determining if the addition of the index data relating to the data file results in a change to any of the index portions or if the index portions are unchanged, wherein an index portion is changed, to add a new entry, or when the predetermined plurality of entries is exceeded to redefine the portion of the index range comprising an index portion;

    storing an index on the sequential storage medium including;

    references to the location of any index portions that are determined to remain unchanged; and

    index portions that are changed to include the index data relating to the data file according to the predetermined order, wherein the index portions are stored in a hierarchical structure of blocks, including at least one final leaf level block, each entry in each said final leaf level block containing the actual address of a data file, andwherein the index includes one or more subsidiary levels each having one or more indexing blocks, each said block in said subsidiary levels including an entry corresponding to at least one block in a higher level.

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