DOS/360 was a compact operating system, intended for use on small mainframes.
Capacity was expensive; one had to be very careful about wasting bytes, whether in RAM (we called it core back then--because it was) or disk (IBMer's called it DASD). A 360 model 40, a good platform for DOS/360, included between 8KB and 256KB of core memory. KB, not MB. All but a few models of System/360 had maximum memory sizes less than 1MB. A 2311 disk held about 6.9MB of data. MB, not GB, which means that five 3 1/2 inch floppy disks would exceed the capacity of the disk pack used in the 2311 drive. The 2314, at four times the 2311 capacity, was still smaller than the hard drives shipping with some of the earliest PCs.
Speed was expensive too. The data transfer rate for a 2311 was 156KB/second, equivalent to 1.25mb/sec, and a 2314 clocked in at 310KB/sec, which is 2.48mb/sec in PC-speak. Compare that to 3gb/sec (SATA-2) on a pc.
Much time was spent, for example, recommending split-cylinder work file extents to minimize disk head movements. Manuals provided recommendations about the best cylinder splits for each language. And recommendations were made to spread files across different disk drives to, again, minimize head movement.
DOS/360 Minimum Hardware Configuration
16,384 bytes of main storage (core memory)
One each: card reader, line printer, card punch
A console printer-keyboard
A disk drive, either 2311 or 2314
One could substitute tape drives for the card reader, line printer, and/or card punch. But I suspect that was useful only if the system was being used with an older system, such as a 1401, that had the card reader, printer, and punch. DOS/360 would be extremely difficult to run with a single disk drive, and 16,384 bytes of memory did not enable many capabilities.
This means that DOS/360 is not set up to operate as a cardless system. As a result, many system maintenance procedures included keying decks of cards, or keying cards to be added to card decks punched from the system. DOS/VS release 33 was the first did support cardless operations.
See how things change when you run DOS/360 on Hercules 390.