Corporate decision makers require access to information from multiple such sources. Setting up queries on individual sources is both cumbersome and（ ）. Moreover, the sources of data may store only current data, whereas decision makers may need access to（ ）data as well. A data warehouse is a repository（or archive）of information gathered from multiple sources, stored under a unified schema, at a（ ）site. Once gathered, the data are stored for a long time, permitting access to historical data.Thus, data warehouses provide the user with a single consolidated（ ）to data, making decision-support queries easier to write.Moreover, by accessing information for decision support from a data warehouse, the decision maker ensures that online transaction-processing systems are not（ ）by the decision-support workloads.
