data set organization

Computing Dictionary

data set organization definition

operating system, storage
(DSORG) An IBM term for file structure. These include PS physical sequential, DA direct access, IS indexed sequential, PO partitioned (a library). This system dates from OS/360, and breaks down beginning with VSAM and VTAM, where it is no longer applied.
Sequential and indexed data sets can be accessed using either a "basic" or a "queued" "access method." For example a DSORG=PS file can use either BSAM (basic sequential access method) or QSAM (queued sequential access method). It can also be processed as a direct file using BDAM. Likewise a library can be processed using BPAM (basic partitioned access method), BSAM, QSAM, or BDAM. DSORG and access method are somewhat, but not completely, orthogonal.
The "basic" access method deals with physical blocks rather than records, and usually provides more control over the specific device. Each I/O operation using the "basic" access method reads or writes a single block. A "basic" read or write starts an asynchronous I/O operation, and the programmer is responsible for waiting for completion and checking for errors.
The "queued" access method deals with logical records and provides blocking and deblocking services. It is "queued" because it provides read-ahead and write-behind services. While a program is processing records in one input block, for example, QSAM may be reading one or more blocks ahead. Queued "get" or "put" operations are synchronous as far as the programmer is concerned. The operation is complete when the next logical record has been successfully processed.
EXCP (Execute Channel Program) is a lower-level method of accessing data.
IBM manuals usually named "Data Administration Guide", e.g. SC26-4505-1 for MVS/ESA DFP 3.1, provide more detail about data set organizations and access methods.
(2005-08-08)
The Free On-line Dictionary of Computing, © Denis Howe 2010 http://foldoc.org
Cite This Source
Explore Dictionary.com
Previous Definition: data set
Next Definition: data stream
More from Thesaurus.com
Synonyms and Antonyms for data set organization
More from Reference.com
Search for articles containing data set organization
Dictionary.com Word FAQs

Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.

Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature