There is an ongoing debate regarding a standard definition for distributed Oracle databases. To Oracle, a distributed database is a geographically distributed system composed entirely of Oracle products. To the GUI/tools vendors, a distributed database is a system that is distributed architecturally, having systems with different architectures and access methods. To the hardware vendors, a distributed database is a system composed of different databases, all running on the same hardware platforms.
In fact, each of these descriptions fits the overall distributed model, but there are some distinguishing characteristics that differentiate a real distributed database from a loosely coupled system.
The standard definition of distributed database has been developed by C. J. Date; he lists 12 specifications for an ideal distributed database:

1. Local autonomy
2. No reliance on a central site
3. Distributed Continuous operation
4. Location independence
5. Fragmentation independence
6. Replication independence
7. Distributed query processing
8. Distributed transaction management
   (update processing)
9. Hardware independence
10. Operating-system independence
11. Network independence
12. Database independence

In the next lesson, we will take a look at Oracle's topology solution to distributed databases.