While creating GDG we we use parameters LIMIT, EMPTY / NOEMPTY, SCRATCH / NOSCRATCH.
I know the meaning of the parameters .
Noempty: Uncataloging oldest gen. of a GDG once the limit is reached.
Empty: Uncataloging all gen. of a GDG once the limit is reached
Scratch : Physically deleting the entry of GDG from the vol. it resides.
NoScratch: Uncatalog the entry of a GDG from the volume that it resides on without physically deleting it.
My question is why both scratch and Empty are both used for uncatalog and deleting the data sets. Is only one parameter required or both required.
Please explain briefly.