The nexus of a data warehouse is the access and storage mechanisms that support it. Typically, this is a relational, multidimensional, or other specialized database designed to facilitate complex queries.
Relational databases are the most popular platform for supporting data warehouses and data marts.
The existence of SQL as a relatively standard query language and ODBC as a common access method has enabled the proliferation of relational databases for analytic applications. And since relational databases can leverage the parallel processing capabilities afforded by highly scalable, multiprocessing Unix platforms, companies are using these data management systems to build terabyte-capacity data warehouses and staging areas. A staging area is a place where companies can load cleansed and integrated operational data before heavily transforming them into specialized data marts. Multidimensional databases are akin to spreadsheets, storing data in a matrix-like structure. In most cases, multidimensional databases are used to support application-specific data marts.