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{{about|mainframe computer file|a general meaning in computing field|Data set}}
In the context of [[IBM]] [[mainframe computer]]s, a '''data set''' (IBM preferred) or '''dataset''' is a [[computer file]] having a [[record-oriented file|record organization]]. Use of this term began with [[OS/360]] and is still used by its successors, including the current [[z/OS]]. Documentation for these systems historically preferred this term rather than ''[[computer file|file]]''.▼
A data set is typically stored on a [[direct access storage device]] (DASD) or [[magnetic tape]],<ref>{{cite web
|url=https://www.ibm.com/support/knowledgecenter/zosbasics/com.ibm.zos.zconcepts/zconcepts_172.htm
|title=What is a catalog?
▲In the context of [[IBM]] [[mainframe computer]]s, a '''data set''' (IBM preferred) or '''dataset''' is a [[computer file]] having a [[record-oriented file|record organization]]. Use of this term began with [[OS/360]] and is still used by its successors, including the current [[z/OS]]. Documentation for these systems historically preferred this term rather than ''[[computer file|file]]''.
Data sets are not unstructured streams of [[byte]]s, but rather are organized in various logical record<ref>{{cite web
▲A data set is typically stored on a [[direct access storage device]] (DASD) or [[magnetic tape]], however unit record devices, such as punch card readers, card punch, and line printers can provide input/output (I/O) for a data set (file).<ref>{{cite web|url=http://publib.boulder.ibm.com/infocenter/zvm/v5r4/index.jsp?topic=/com.ibm.zvm.v54.hcpa7/hcse7b3050.htm|title=IBM Knowledge Center - Home of IBM product documentation|website=publib.boulder.ibm.com}}</ref>
|url=https://www.ibm.com/support/knowledgecenter/zosbasics/com.ibm.zos.zconcepts/zconc_datasetintro.htm
Records in a dataset may be fixed or variable length.<ref>{{cite web
▲Data sets are not unstructured streams of [[byte]]s, but rather are organized in various logical record and block structures determined by the <code>DSORG</code> (data set organization), <code>RECFM</code> (record format), and other parameters. These parameters are specified at the time of the data set allocation (creation), for example with [[Job Control Language]] <code>DD</code> statements. Inside a job they are stored in the [[Data Control Block]] (DCB), which is a data structure used to access data sets, for example using [[access method]]s.
|url=https://www.ibm.com/support/knowledgecenter/zosbasics/com.ibm.zos.zconcepts/zconcepts_159.htm
|title=Data set record formats
|quote=Records are either fixed length or variable length in a given data set.}}</ref>
==Data set organization==
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