Terminology and overview

Formally, "database" refers to the data
themselves and supporting data structures.
Databases are created to operate large
quantities of information by inputting, storing,
retrieving and managing that information.
Databases are set up so that one set of
software programs provides all users with
access to all the data.
A "database management system" (DBMS) is a
suite of computer software providing the
interface between users and a database or
databases. Because they are so closely related,
the term "database" when used casually often
refers to both a DBMS and the data it
manipulates.
Outside the world of professional information
technology, the term database is sometimes
used casually to refer to any collection of data
(perhaps a spreadsheet , maybe even a card
index). This article is concerned only with
databases where the size and usage
requirements necessitate use of a database
management system. [1]
The interactions catered for by most existing
DBMSs fall into four main groups:
Data definition – Defining new data
structures for a database, removing data
structures from the database, modifying the
structure of existing data.
Update – Inserting, modifying, and deleting
data.
Retrieval – Obtaining information either for
end-user queries and reports or for processing
by applications.
Administration – Registering and monitoring
users, enforcing data security, monitoring
performance, maintaining data integrity, dealing
with concurrency control, and recovering
information if the system fails.
A DBMS is responsible for maintaining the
integrity and security of stored data, and for
recovering information if the system fails.
Both a database and its DBMS conform to the
principles of a particular database model . [2]
"Database system" refers collectively to the
database model, database management system,
and database. [3]
Physically, database servers are dedicated
computers that hold the actual databases and
run only the DBMS and related software.
Database servers are usually multiprocessor
computers, with generous memory and RAID
disk arrays used for stable storage. RAID is
used for recovery of data if any of the disks fail.
Hardware database accelerators, connected to
one or more servers via a high-speed channel,
are also used in large volume transaction
processing environments. DBMSs are found at
the heart of most database applications . DBMSs
may be built around a custom multitasking
kernel with built-in networking support, but
modern DBMSs typically rely on a standard
operating system to provide these
functions. [ citation needed ] Since DBMSs
comprise a significant economical market ,
computer and storage vendors often take into
account DBMS requirements in their own
development plans. [ citation needed ]
Databases and DBMSs can be categorized
according to the database model(s) that they
support (such as relational or XML), the type(s)
of computer they run on (from a server cluster
to a mobile phone), the query language (s) used
to access the database (such as SQL or
XQuery ), and their internal engineering, which
affects performance, scalability , resilience, and
security.