JCL support for z/OS UNIX

JCL data definition (DD) statements use a data definition name (ddname) to specify the data to be used by the program that you are submitting as a batch job. The ddname is used in two places:

In your application program. Here the ddname refers to nonspecific data, rather than a specific data set name or path name.
In the JCL used to submit the application program as a background job. Here it binds the nonspecific reference in the program to a specific data set name or path name.

You can specify a z/OS UNIX file in the JCL for user-written applications or for IBM-supplied services, such as:

DFSMS, Program Management Binder, a prelinker, or a linkage editor
BPXBATCH
The TSO/E OCOPY command

Note: In this discussion, references to JCL also apply to the equivalent dynamic allocation functions.