Atomicity: all actions are carried out, or none

Consistency: each transaction preserves the consistency of the database if executed by itself

• many consist. states
• e.g. transfer money, the total is the same - consist.
  T1 : Transf. $1000 from A to B
  -----R(A) W(A) R(B) W(B)
  T2 : same as T1
  ++ Serial Schedule

Isolation:

Isolation refers to the requirement that other operations cannot access or see the data in an intermediate state during a transaction. This constraint is required to maintain the performance as well as the consistency between transactions in a DBMS.

Duability :

Durability refers to the guarantee that once the user has been notified of success, the transaction will persist, and not be undone. This means it will survive system failure, and that the database system has checked the integrity constraints and won't need to abort the transaction. Many databases implement durability by writing all transactions into a transaction log that can be played back to recreate the system state right before a failure. A transaction can only be deemed committed after it is safely in the log.