Data warehouses, in contrast, are targeted for decision
support. Historical, summarized and consolidated data is
more important than detailed, individual records. Since data
warehouses contain consolidated data, perhaps from several
operational databases, over potentially long periods of time,
they tend to be orders of magnitude larger than operational
databases; enterprise data warehouses are projected to be
hundreds of gigabytes to terabytes in size. The workloads are
query intensive with mostly ad hoc, complex queries that can
access millions of records and perform a lot of scans, joins,
and aggregates. Query throughput and response times are
more important than transaction throughput.