How does DMA increase system concurrency

How does DMA increase system concurrency? How does it complicate
hardware design?
Answer: DMA increases system concurrency by allowing the CPU
to perform tasks while the DMA system transfers data via the system
and memory buses. Hardware design is complicated because the DMA
controller must be integrated into the system, and the system must
allow the DMA controller to be a bus master. Cycle stealing may also
be necessary to allow the CPU and DMA controller to share use of the
memory bus.