Fragmentation independence refers to the ability of end users to store logically related information at different physical locations. There are two types of fragmentation independence: vertical partitioning and horizontal partitioning. Horizontal partitioning allows for different rows of the same table to be stored at different remote sites. This is commonly used by organizations that maintain several branch offices, each with an identical set of table structures. Vertical partitioning refers to the ability of a distributed system to fragment information such that the data columns from the same logical tables are maintained across a network.

Replication Independence

Replication is the ability of a database to create copies of a master database at remote sites. These copies are called snapshots within Oracle, and a snapshot may contain the entire database or any component of a database. For example, in an Oracle data warehouse, a fact table may be replicated by geographic region, and copies of subsets of the fact tables could reside at different locations for the northern region, southern region, and so on. Remember, disk space is cheap, and data warehouse replication at different geographic locations can dramatically improve response times for end users. In addition, subsets of a fact table may be specified, such that only specific rows and columns appear in a replicated table, and the replicated items are refreshed on a periodic basis.

This is an excerpt from "High Performance Data Warehousing".

If you like Oracle tuning, you may enjoy the book Oracle Tuning: The Definitive Reference , with over 900 pages of BC's favorite tuning tips & scripts.  You can buy it directly from the publisher and save 30%, and get instant access to the code depot of Oracle tuning scripts.