Databases Reference
In-Depth Information
To facilitate the effective use of the DB hardware and software
resources, the DB administrator (DBA) is necessary. This person (or group
of persons) has a fundamental role in the performance of the global DB sys-
tem. The DBA is also responsible for protecting the DB as a resource shared
by all the users. Among other duties, the DBA must carry out backup, recov-
ery, and reorganization; provide DB standards and documentation; enforce
data activity policy; control redundancy; maintain configuration control;
tune the DB system; and generate and analyze DB performance reports.
Physical design and performance tuning are key aspects and essential to the
success of a DB project. The changes in the performance dimension also
oblige the introduction of important transformations in the DBA functions
[25]. The role of the DBA in the future will be increasingly difficult, and
DBMS products will have to offer, increasingly, facilities to help the DBA in
DB administration functions.
1.4.2
Distribution and Integration
In the last decade, the first distributed DBMSs appeared on the market and
have been an important focus of DB research and marketing. Some achieve-
ments of the early distributed products were two-phase commit, replication,
and query optimization.
Distributed DBs (see Chapter 9) can be classified into three areas: dis-
tribution, heterogeneity, and autonomy [26]. In the last area, federated DBs
(semiautonomous DBs) and multidatabases (completely autonomous) can
be found. A higher degree of distribution is offered by mobile DBs (see
Chapter 10), which can be considered distributed systems in which links
between nodes change dynamically.
From that point of view, we must also emphasize the integration of
DBs and the Internet and the World Wide Web. The Web adds new compo-
nents to DBs, including a new technology for the graphical user interface
(GUI), a new client/server model (the hypertext transfer protocol, HTTP),
and a hyperlink mechanism between DBs [27].
New architectures capable of connecting different software compo-
nents and allowing the interoperation between them are needed. Database
architectures must provide extensibility for distributed environments, allow
the integration of legacy mainframe systems, client/server environments,
Web-based applications, and so on.
Vendors now offer enough of the integration facilities required to
access distributed DBs from all types of devices (personal computers, PDAs,
palmtops, laptops, etc.) and some support for Internet data. However,
