Oracle not only scales through deployment on increasingly powerful
single platforms, but also can be deployed in distributed configurations. Oracle
deployed on multiple platforms can be combined to act as a single logical distributed
database.
This section describes some of the basic ways that Oracle handles database interactions
in a distributed database system.
Distributed Queries and Transactions
Data within an organization is often spread among multiple databases for reasons of
both capacity and organizational responsibility. Users may want to query this distributed
data or update it as if it existed within a single database.
Oracle first introduced distributed databases in response to the requirements for
accessing data on multiple platforms in the early 1980s. Distributed queries can
retrieve data from multiple databases. Distributed transactions can insert, update, or
delete data on distributed databases. Oracle??™s two-phase commit mechanism,
described in Chapter 13, guarantees that all the database servers that are part of a
transaction will either commit or roll back the transaction.
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