Sections 19.4 and 21.3

The ACID properties of transactions

-must be guaranteed by a TPS in the presence of concurrency

and unpredictable failures.

Atomicity

Either all or none of the transaction's operations are performed.

This must be ensured by the recovery manager.

A crash may occur part way through a transaction and the

invocations of any incomplete transactions must be undone.

Consistency

A transaction transforms the system from one consistent state to another.

This is achieved through concurrency control, provided that atomicity is

guaranteed by the recovery manager in the presence of crashes.

Isolation

An incomplete transaction cannot reveal its result to other

transactions before it is committed.

This is achieved through concurrency control.

Durability

Once a transaction is committed the system must guarantee that the results

of its operations will persist, even if there are subsequent system failures.

This is the responsibility of the recovery manager, based

on general data management policies.