Originally posted by: Cecilia_F

z/OS supports simplified processing of multiple versions of related data. The sequences of different generations of data or updates to the data are known as generation data groups (GDGs). Each data set in the group is called a generate data set (GDS) or simply generation.

On AIX, “file” is the equivalent term for “data set” on z/OS. Grouping related files offers the following advantages:

All of the files in the group can be referred to by a common name

The files in the group are kept in generation order.

Outdated generations can be automatically discarded.

For COBOL for AIX, V4.1, GDG functions such as resolution of relative GDG names to their absolute equivalents, automatic addition of new generations, and deletion of outdated generations to the group are provided by enhancements to the COBOL for AIX runtime library. Emulation of the z/OS build-in GDG catalog and generation management support is provided by a utility that is called ‘gdgmgr’.

You can find more information about the GDG support in COBOL for AIX Programming Guide:

https://www.ibm.com/support/knowledgecenter/en/SS6SGM_5.1.0/com.ibm.cobol51.aix.doc/PGandLR/concepts/cpfio75.html