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