With the mainframe all disks are external. This diagram [0] does a good job of showing that. [0] https://en.wikipedia.org/wiki/Count_key_data#/media/File:IBM_C

With the mainframe all disks are external. This diagram [0] does a good job of showing that. [0] https://en.wikipedia.org/wiki/Count_key_data#/media/File:IBM_CKD_Arch.png https://en.wikipedia.org/wiki/Count_key_data#/media/File:IBM...