Naming Generation Data Groups for ISO/ANSI Version 3 or Version 4 Labels

In a Version 3 or Version 4 ISO/ANSI label (LABEL=(,AL)), the generation number and version number are maintained separately from the file identifier. Label processing removes the generation number and version number from the generation data set name. The generation number is placed in the generation number field (file label 1 positions 36 through 39), and the version number is placed in its position on the same label (position 40 and 41). The file identifier portion of a Version 3 or Version 4 ISO/ANSI label contains the generation data set name without the generation number and version number.

For Version 3 or Version 4 labels, you must observe the following specifications created by the GDG naming convention.

Data set names whose last 9 characters are of the form .GnnnnVnn (n is 0 through 9) can only be used to specify GDG data sets. When a name ending in .GnnnnVnn is found, it is automatically processed as a GDG. The generation number Gnnnn and the version number Vnn are separated from the rest of the data set name and placed in the generation number and version number fields.
Tape data set names for GDG files are expanded from a maximum of 8 user-specified characters to 17 user-specified characters. (The tape label file identifier field has space for 9 additional user-specified characters because the generation number and version number are no longer contained in this field.)
A generation number of all zeros is not valid, and is treated as an error during label validation. The error appears as a "RANG" error in message IEC512I (IECIEUNK) during the label validation installation exit.
In an MVS system-created GDG name, the version number is always be 0. (MVS does not increase the version number by 1 for subsequent versions.) To obtain a version number other than 0, you must explicitly specify the version number (for example, A.B.C.G0004V03) when the data set is allocated. You must also explicitly specify the version number to retrieve a GDG with a version number other than 0.
Because the generation number and version number are not contained on the identifier of HDR1, generations of the same GDG have the same name. Therefore, an attempt to place more than one generation of a GDG on the same volume results in an ISO/ANSI standards violation in a system supporting Version 3 and MVS enters the validation installation exit.