What is Atomicity

The phrase "all or nothing" succinctly describes the first ACID property of atomicity. When an update occurs to a database, either all or none of the update becomes available to anyone beyond the user or application performing the update. This update to the database is called a transaction and it either commits or aborts. This means that only a fragment of the update cannot be placed into the database, should a problem occur with either the hardware or the software involved. Features to consider for atomicity:

 

	A transaction is a unit of operation - either all the transaction's actions are completed or none are
	Atomicity is maintained in the presence of deadlocks
	Atomicity is maintained in the presence of database software failures
	Atomicity is maintained in the presence of application software failures
	Atomicity is maintained in the presence of CPU failures
	Atomicity is maintained in the presence of disk failures
	Atomicity can be turned off at the system level
	Atomicity can be turned off at the session level