As an alternative to using absolute generation and version numbers when cataloging or referring to a generation, you can use a relative generation number. To specify a relative number, use the GDG name followed by a negative integer, a positive integer, or a 0, enclosed in parentheses. For example, A.B.C(-1). A.B.C(+1), or A.B.C(0).

The value of the specified integer tells the operating system what generation number to assign to a new generation, or it tells the system the location of an entry representing a previously cataloged generation.

When you use a relative generation number to catalog a generation, the operating system assigns an absolute generation number and a version number of V00 to represent that generation. The absolute generation number assigned depends on the number last assigned and the value of the relative generation number that you are now specifying. For example if, in a previous job generation, A.B.C.G0005V00 was the last generation cataloged, and you specify A.B.C(+1), the generation now cataloged is assigned the number G0006V00.

Though any positive relative generation number can be used, a number greater than 1 can cause absolute generation numbers to be skipped. For example, if you have a single step job, and the generation being cataloged is a +2, one generation number is skipped. However, in a multiple-step job, one step might have a +1 and a second step a +2, in which case no numbers are skipped.