The data can be on different servers running different operating systems or even
different database management systems. The data needed to answer any specific
business question may need to be accessed from more than one server. A user may
need to access this separate 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 across 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 examines both of these options and the technologies associated
with each solution.
Accessing Multiple Databases As a Single Entity
Users sometimes need to query or manipulate data that resides in multiple Oracle
databases or in a mixture of Oracle and non-Oracle databases. This section describes
a number of techniques and architectures you can use to interact with data in a distributed
environment.
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