Cataloging Generation Data Groups

Also, in a multiple-step job, you should catalog or uncatalog data sets using JCL rather than IEHPROGM or a user program. Because data set allocation and unallocation monitors data sets during job execution and is not aware of the functions performed by IEHPROGM or user programs, data set orientation might be lost or conflicting functions might be performed in subsequent job steps.

When you use a relative generation number to refer to a generation that was previously cataloged, the relative number has the following meaning:

A.B.C(0) refers to the latest existing cataloged entry.
A.B.C(-1) refers to the next-to-the-latest entry, and so forth.

When cataloging is requested using JCL, all actual cataloging occurs at step termination, but the relative generation number remains the same throughout the job. The following results can occur:

A relative number used in the JCL refers to the same generation throughout a job.
A job step that ends abnormally can be deferred for a later step restart. If the job step successfully cataloged a generation data set in its GDG, you must change all relative generation numbers in the next steps using JCL before resubmitting the job.

For example, if the next steps contained the following relative generation numbers:

A.B.C(+1) refers to the entry cataloged in the terminated job step, or
A.B.C(0) refers to the next to the latest entry, or
A.B.C(-1) refers to the latest entry, before A.B.C(0).

You must change A.B.C(+1) to A.B.C(0), A.B.C(0) to A.B.C(-1), and A.B.C(-1) to A.B.C(-2) before restarting the step.