• the process of ensuring persisting transaction permanently and do not accidentally disappear or get erased even during a database crash.
  • durability actions are slow because to make things durable that means you write to disk and writing to the disk is slow.
  • this means changes made by committed transactions must be persisted in a durable non-volatile storage.
  • most of DBMSs bypass the os cache to ensure durability by fsync os which can be expensive and slow down commits.