Database Reference
In-Depth Information
2.4 The Database Management System
The database management system (DBMS) is the software that facilitates management
of the database. When a user issues a request via some DSL (for example SQL), it is the
DBMS that interprets the request, executes the appropriate instructions and responds to
the user.
Functions of the DBMS include the following:
•
Data definition (relation, dependencies, integrity constraints,
views, etc.)
•
Data manipulation (adding, updating, deleting, retrieving,
reorganizing, and aggregating data)
•
Data security and integrity checks
•
Management of data access (including query optimization),
data recovery and concurrency
•
Maintenance of a user-accessible system catalog (data dictionary)
•
Support of miscellaneous non-database functions (e.g. utilities
such as copy)
•
Programming language support
•
Transaction management (either all updates are made or
none is made)
•
Backup and recovery services
•
Communication support (allow the DBMS to integrate with
underlying communications software)
•
Support for interoperability including open database
connectivity (ODBC), Java database connectivity (JDBC), and
other related issues
Optimum efficiency and performance are the hallmarks of a good DBMS. To
illustrate the critical role of the DBMS, consider the steps involved when an application
program accesses the database:
1.
Program-A
issues a request to the DBMS (expressed in terms
of sub-schema language);
2.
DBMS looks at
Program-A
sub-schema, schema and physical
description (these information are stored in tables);
3.
DBMS determines which files must be accessed, which
records are needed and how access is done;
4.
DBMS issues instruction(s) (reads or writes) to the
operating system;
