What is "data set"

n. 1 (context computing English) a file of related records on a computer-readable medium such as disk, especially one on a mainframe computer; a dataset 2 (context telecommunications English) a modem (that connects a device such as a teletype to an ordinary telephone) 3 (context statistics English) A set of data to be analyzed.

A data set (or dataset) is a collection of data.

Most commonly a data set corresponds to the contents of a single database table, or a single statistical data matrix, where every column of the table represents a particular variable, and each row corresponds to a given member of the data set in question. The data set lists values for each of the variables, such as height and weight of an object, for each member of the data set. Each value is known as a datum. The data set may comprise data for one or more members, corresponding to the number of rows.

The term data set may also be used more loosely, to refer to the data in a collection of closely related tables, corresponding to a particular experiment or event. An example of this type is the data sets collected by space agencies performing experiments with instruments aboard space probes.

In the open data discipline is the unit to measure the information released in a public open data repository. The European Open Data portal aggregates more than half a million datasets. In this field other definitions have been proposed but currently there is not an official one. Some other issues (real-time data sources, non-relational datasets, etc) increases the difficult to reach a consensus about it.

In the context of IBM mainframe computers, a data set (IBM preferred) or dataset is a computer file having a 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 file.

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).

Data sets are not unstructured streams of bytes, but rather are organized in various logical record and block structures determined by the DSORG (data set organization), RECFM (record format), and other parameters. These parameters are specified at the time of the data set allocation (creation), for example with Job Control Language DD 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 methods.