By defining a GenerationDataGroup you have to specify a Limit. That's the number of max generations you can create in order. By reaching the max, a turn around will happen and the oldest one will become the newest one.
With every create of a GDG, for ex. DSN=HUGO you code in JCL:
//OUTPUT DD DSN=HUGO(+1)
So now a File is created with DSN HUGO.G000V01
By next run, it's HUGO.G000V02 and then HUGO.G000V03
You could simply use TSO 3.4 with HLQ of your DSN to see all allocated
In my ex. here HUGO.G000V03 is the latest one, wich also means the newest one.