If the DUPLICATES phrase is specified, and the contents of all the key
elements associated with one record are equal to the corresponding key elements
in one or more other records, the order of these records is as follows:
- The order of the associated input files as specified in the SORT statement.
Within a given file the order is that in which the records are accessed from
that file.
- The order in which these records are released by an input procedure, when
an input procedure is specified.
If the DUPLICATES phrase is not specified, the order of these records is
undefined.