In the example system, there are two groups of tape devices, again
duplicated in both figures. These devices are used for dump volumes,
ML2 volumes, and backup volumes. ML2 and backup volumes can also use
DASD.
Figures
Figure 1,
Figure 2, and
Figure 1 show
two groups of cartridge-type devices: those with cartridge loaders,
and those without. The cartridge-type devices without cartridge loaders
are used (in the example) mainly as input devices for recall and recovery
because recall or recovery is always from a specific tape. The cartridge-type
devices with cartridge loaders are used for output to backup, dump,
and ML2 tapes because output can use scratch tapes (tapes that no
longer contain valid data, and have been returned to the global scratch
pool) and take advantage of the cartridge loader’s ability to change
tapes automatically.
Note: Cartridge-type devices may be in an MTL
or an ATL.