We simply allow interleaving of atomic actions, whose atomicity plays a vital role in the system.
In other words, atomicity means "indivisibility" and "irreducibility".
Atomicity is commonly enforced by mutual exclusion, whether at the hardware level building on a cache coherency protocol, or the software level using semaphores or locks.
Atomic commitment protocols are intended and designed to achieve atomicity without considering database concurrency control.
The atomicity of these elements is not specifically mentioned and it appears that they were actually taken to be continuous.
Finally, atomicity itself relies on durability to ensure the atomicity of transactions even in the face of external failures.
In write ahead logging, atomicity is guaranteed by copying the original (unchanged) data to a log before changing the database.
Transaction consistency is also frequently referred to as atomicity.
