Atomicity

Atomicity states the mode, in which either all or no modifications are written to the database. In this mode each transaction is said to be "atomic". If any part of the transaction fails, the whole transaction will fail too. For example, in a bank transfer transaction there are 2 parts: debit and credit. If the debit operation was successful, but the credit failed, the whole transaction should fail and the system should remain in the initial state.

Some of the atomicity features:

• 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 operation system failures
• atomicity is maintained in the presence of CPU failures
• atomicity is maintained in the presence of disk failures