Data set (IBM mainframe)

IBM mainframe term for a file.

Unlike UNIX files, they are not unstructured streams of bytes, but rather come in various block structures determined by the DSORG (data set organisation) parameter of the JCL which allocated them.

e.g. PDS = Partioned Data Set (dataset divided into partions, each of which holds a separate sub-data set -- kind of like a directory in other systems)