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Author Mullin, James K.
Source ACM Digital Library
Content type Text
Publisher Association for Computing Machinery (ACM)
File Format PDF
Language English
Subject Keyword Cylinder ♦ Isam ♦ Index sequential ♦ Hashing ♦ Disk ♦ Overflow ♦ Scatter storage
Abstract The Index Sequential Access Method (ISAM) is one of the most important file management systems used with moveable head disk devices. This study investigates the use of an unconventional method of treating overflow records. The method is to use hashing techniques to allocate space for such records. If certain conditions are satisfied, this is superior to the conventional ISAM method of chaining the overflow records via linked list techniques. These conditions are: long overflow chains with significant overflow; lack of tight disk space constraints; record keys which are small compared to the total record size; and significant use of the file in the index as opposed to the sequential mode. Using hashed overflow, the time to locate a record is dependent not on the total volume of overflow records as in conventional ISAM, but on the percentage use of space dedicated to overflow records.
Description Affiliation: Univ. of Western Ontario, London, Ont., Canada (Mullin, James K.)
Age Range 18 to 22 years ♦ above 22 year
Educational Use Research
Education Level UG and PG
Learning Resource Type Article
Publisher Date 2005-08-01
Publisher Place New York
Journal Communications of the ACM (CACM)
Volume Number 15
Issue Number 5
Page Count 7
Starting Page 301
Ending Page 307


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Source: ACM Digital Library