Oracle Essentials: Oracle9i, Oracle8i and Oracle8, Second Edition

Chapter 12. Distributed Databases and Distributed Data

Data in large and midsized 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 nature of the 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 each of these options and the technologies associated with each solution. Several of the technologies described here can be used in combination with other Oracle9iAS components to integrate data from several sources (for example, Oracle Workflow might be used to initiate and perform this integration in a specific order). This combination of Oracle technology solutions is sometimes referred to as the Oracle Integration Server (OIS).

Accessing Multiple Databases as a Single Entity

Users sometimes need to query or manipulate data that resides in multiple ...