Chapter 12. Distributed Databases and Distributed Data
Data in large and mid-sized companies frequently resides on multiple
servers. The data might be distributed across various-sized servers
running a mix of operating systems for a number of reasons, including
scalability, performance, access, and management. As a result, the
data needed to answer business questions may not reside on a single
local server. The user may need to access data on several servers
simultaneously, or the data required for an answer may need to be
moved to a local server. Inserts, updates, or deletions of data on
these distributed servers may also be necessary.
There are two basic ways to deal with data in distributed databases:
as part of a single distributed entity in which the distributed
architecture is transparent, or by using a variety of replication
techniques to create copies of the data in more than one location.
This chapter will examine both of these options and the technologies
associated with each solution. Several of the technologies described
here can be used in combination with Oracle Application Server
components to integrate data from several sources (for example, to
facilitate document exchange). This combination of Oracle technology
solutions is sometimes referred to as the Oracle Enterprise
Integration framework.
Grid computing introduces a new third solution to widely distributed
data�a single database deployment model leveraging
Oracle's Real Application Clusters and Application
Server services. As might be expected, capabilities introduced
earlier for distributed data play a part in this solution,
particularly Oracle Streams, as described later in this chapter.
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