Sequential record values allow you to use keyed access on a sequential data set associated with a KEYED SEQUENTIAL file.
You cannot construct or manipulate sequential record values in PL/I; you can, however, compare their values in order to determine the relative positions of records within the data set. Sequential record values are not normally printable.
You can obtain the sequential record value for a record by using the KEYTO option, either on a WRITE statement when you are loading or extending the data set, or on a READ statement when the data set is being read. You can subsequently use a sequential record value obtained in either of these ways in the KEY option of a READ or REWRITE statement.