Once you've built a data warehouse topology, you could deploy multiple Oracle databases to implement the data warehouse and its data marts. Enterprise-wide warehouses are more common on Unix servers and are beginning to appear on clustered (RAC) Linux platforms. Smaller data marts are common on Windows and Linux. Many organizations are increasingly consolidating data marts and enterprise data warehouses on the more scalable platforms.
Oracle Enterprise Manager provides a common GUI for managing these multiple instances regardless of the underlying operating system. EM is browser-based with a multiuser repository for tracking and managing the Oracle instances. (EM is discussed in much more detail in Chapter 5.)
In warehousing, in addition to basic management, ongoing tuning for performance is crucial. Enterprise Manager 10g supports many of the automated diagnostics and tuning features in Oracle Database 10g.
Within the largest warehouses and data marts, you may want to manage or maintain availability to some of the data even as other parts of the database are moved offline. Oracle's Partitioning option enables data partitions based on business value ranges (such as date) or discrete values for administrative flexibility, while enhancing query performance through the cost-based optimizer's ability to eliminate access to non-relevant partitions. As an example, "rolling window" administrative operations are used to add new data and remove old data based on ranges of time. A new partition can be added, loaded, and indexed in parallel, and optionally removed, all without impacting access to existing data.
Range partitioning first became available as an Oracle8 option. Hash partitioning was added to the Oracle8i Partitioning option enabling the spread of data evenly based on a hash algorithm for performance. Hashing may be used within range partitions (composite partitioning) to increase the performance of queries while still maintaining the manageability offered by range partitioning. Oracle9i introduced "List" partitioningpartitions based on discrete values such as geographies. A composite partitioning type of Range-List, such that you can partition by dates within geographies, first appeared in Oracle9i Release 2.