atomic write
Writing a new copy elsewhere, then switching one small pointer, so data is either all old or all new.
An atomic write makes an update appear all-or-nothing, typically by writing the new copy to a fresh location and then switching a small, checksummed pointer in one step.
Examples
Settings saved into two record slots A and B as
{seq, data, crc}: the save overwrites the lower-sequence slot, and loading takes the higher valid one.The A/B app slots plus otadata's checksummed switch make a firmware update an atomic write at the scale of a whole image.
See also