Data Models
A representation, usually graphic, of a complex “real-world” data structure.
Database Languages
Database languages, compared with general-purpose languages, have only a limited expressive power.
The DBMS query language can be embedded in a general-purpose language which ensures full computational power.
Transactions Control
A transaction is a logical unit of work; that is, it must be entirely completed or aborted—no intermediate ending states are accepted.
All transactions must have the following properties:
Atomicity
requires that, unless all operations (parts) of a transaction are completed, the transaction is aborted.
Durability
assures that, once a transaction is completed, the database reaches a consistent state; that state can not be lost, even in the event of a system failure.
Serializability
ensures that the selected order of transaction operations creates a final database state that would have been produced if the transactions are executed in a serial fashion.
Isolation
assures that data used during the execution of a transaction can not be used by a second transaction until the first one is completed.
†Concurrency control
is a DBMS feature that is used to coordinate the simultaneous execution of transactions in a multiprocessing database system while preserving data integrity.
Data Structures
An integral component of the database system is a secondary storage management facility, which mostly uses B-trees.