Databases Reference
In-Depth Information
resource managers. Although these individuals often have the vision to
recognize the long-term benefit of a distributed DBMS environment to an
organization, they must rely on the participation and input of those in the
organization who are directly involved with the business functions and use
information to make decisions and manage operations. There must be con-
siderable interaction among many different people in the organization,
each of whom provides feedback to validate and refine the plans.
Strategic planning must first provide a sufficient justification for the
expenditure of resources necessary to migrate to a distributed environ-
ment. Only after this justification has been accepted and fully approved by
senior management can the task of initiating projects to design, develop,
and implement a distributed DBMS environment and applications start.
OVERALL DESIGN OF DISTRIBUTED DATABASE STRATEGY
A distributed database environment consists of a collection of sites or
nodes, connected by a communications network. Each node has its own
hardware, central processor, and software which may, or may not, include
a database management system. The primary objective of a distributed
DBMS is to give interactive query users and application programs access to
remote data as well as local data.
Individual nodes within the distributed environment can have different
computing requirements. Accordingly, these nodes may have different
hardware, different software, and they may be connected in many different
ways. Some of the variations possible in the distributed database environ-
ment are discussed in the following sections.
Client/Server Computing
The most basic distributed capability is Remote Database access from
single users at a node. A node may be a mainframe, a minicomputer, or a
microcomputer (personal computer). The node that makes the database
access request is referred to as a client node, and the node that responds
to the request and provides database services is referred to as the server
node. The association is limited to the two parties involved — the client
and the server.
Exhibit 1 represents several different configurations available under a
client/server computing environment. The following are descriptions of
the different configurations shown in the exhibit.
The operating environment of an individual
node can be single-user or multiuser, depending on the operating system of
that node. In a single-user operating environment, a node can be only a cli-
ent. Such a node may or may not have databases. For non-database client
nodes, the software typically consists of front-end application programs
Client Single User Node.
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