Once the DBMS informs the user that a transaction has been successfully…

Key idea: Once the DBMS reports a transaction as successfully completed, its effects must be permanent even if the system crashes — this property is called durability.

• Durability: committed changes survive crashes and are stored on non-volatile media. Systems implement this using techniques like write-ahead logging and flushing the commit record to disk before acknowledging the commit.

• Atomicity: ensures a transaction is all-or-nothing (either fully applied or fully rolled back).

• Consistency: ensures transactions preserve database integrity constraints, moving the database from one valid state to another.

• Isolation: ensures concurrent transactions do not interfere and that results are equivalent to some serial order of execution.