Indexed Sequential Access Method
Indexed sequential file; ISAM file; ISAM
An indexed sequential access method is a static, hierarchical, disk-based index structure that enables both (single-dimensional) range and membership queries on an ordered data file. The records of the data file are stored in sequential order according to some data attribute(s). Since ISAM is static, it does not change its structure if records are added or deleted from the data file. Should new records be inserted into the data file, they are stored in an overflow area. Deleted records are removed from the file (leaving empty space).
Although transparent for the user of a DBMS, access methods play a key role in database performance. A major performance goal of a DBMS is to minimize the number of I/Os (i.e., blocks or pages transferred) between the disk and main memory. One way to achieve this goal is to minimize the number of I/Os when answering queries. Note that many q ...
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- Indexed Sequential Access Method
- Reference Work Title
- Encyclopedia of Database Systems
- pp 1435-1438
- Print ISBN
- Online ISBN
- Springer US
- Copyright Holder
- Springer US
- Additional Links
- Industry Sectors
- eBook Packages
- Editor Affiliations
- 1. College of Computing, Georgia Institute of Technology
- 2. Database Research Group David R. Cheriton School of Computer Science, University of Waterloo
- Author Affiliations
- 1. University of Athens, Athens, Greece
- 2. University of California-Riverside, Riverside, CA, USA
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