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Indexed Available Access Method for File Organization

IP.com Disclosure Number: IPCOM000075608D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Edwards, RL: AUTHOR [+2]

Abstract

An indexed available access method for a file organization utilizes three file elements for the storage of records within a data file. A record is placed in the first location in the main file, large enough to contain it.

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Indexed Available Access Method for File Organization

An indexed available access method for a file organization utilizes three file elements for the storage of records within a data file. A record is placed in the first location in the main file, large enough to contain it.

A main data file 11 is divided so as to contain two data blocks per track. Within each block are a variable number of records, the number of records depending upon the length of each individual record. An availability table 13 indicates the amount of space available in each block for the recording of further records. An index table 15 contains a location entry for each index key. The location entry is specified as a track and record number.

In order to retrieve records, the high-level index is first read to determine the location of the detail index which specifies the location of the data. In order to add records, the availability is read to determine if there is a block containing sufficient space for the record. The first such block containing sufficient space specified by the availability table is utilized to receive the record. Once the record is written, the availability table is updated, and the new index entries are inserted in the index table 15. When a record is deleted, it is first retrieved, as described above, and thereafter removed from the block which is repacked. The availability table 13 is then updated and the entry is deleted from the index.

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