Data Persistence
Data persistence means that in a DBMS all data is maintained as long as
it is not deleted explicitely. The life span of data needs to be determined
directly or indirectly be the user and must not be dependent on system features.
Additionally data once stored in a database must not be lost.
Changes
of a database which are done by a transaction are persistent. When a transaction
is finished even a system crash cannot put the data in danger.