Examine the features of the leading commercial RDBMSs. As data warehousing becomes more prevalent, you would expect to see data warehouse features being included in the software products. That is exactly what the database vendors are doing. Data-warehouse-related add-ons are becoming part of the database offerings. The database software that started out for use in operational OLTP systems is being enhanced to cater to decision support systems. DBMSs have also been scaled up to support very large databases.
Some RDBMS products now include support for the data acquisition area of the data warehouse. Mass loading and retrieval of data from other database systems have become easier. Some vendors have paid special attention to the data transformation function. Replication features have been reinforced to assist in bulk refreshes and incremental loading of the data warehouse.
Bit-mapped indexes could be very effective in a data warehouse environment to index on fields that have a smaller number of distinct values. For example, in a database table containing geographic regions, the number of distinct region codes is few. But frequently, queries involve selection by regions. In this case, retrieval by a bit-mapped index on the region code values can be very fast. Vendors have strengthened this type of indexing. We will discuss bit-mapped indexing further in Chapter 18.
Apart from these enhancements, the more important ones relate to load balancing and query performance. ...