DataWarehouse :
Data warehouse is record of an enterprise's past transactional and operational information, stored in a database designed to favour efficient data analysis and reporting (especially OLAP).
Data warehousing is not meant for current "live" data. Data warehouses often hold large amounts of information which are sometimes subdivided into smaller logical units called dependent datamarts.
Usually ,two basic ideas guide th creation of a data warehouse:
>Integration of data from distributed and differently structures databases,which facilitates a global overview and comprehensive analysis in the data warehouse.
>Separation of data used in daily operations from data used in the data warehouse for purposes of reporting, decision support, analysis and controlling.
Periodically, one imports data from enterprise resource planning (ERP ) systems and other related business software systems into the data warehouse for further processing. It is common practice to "stage" data prior to merging it into a data warehouse. In this sense, to "stage data" means to queue it for preprocessing, usually with an ETL tool. The preprocessing program reads the staged data (often a business's primary OLTP databases), performs qualitative preprocessing or filtering (including denormalization, if deemed necessary), and writes it into the warehouse.
A database designed to support decision making in an organization. Data from the production databases are copied to the data warehouse so that queries can be performed without disturbing the performance or the stability of the production systems.
Data storage of consolidated information dedicated to easely and quickly provide simple or pre-aggregated data for analysis
A data warehouse is, primarily, a record of an enterprise's past transactional and operational information, stored in a database designed to favour efficient data analysis and reporting (especially OLAP). Data warehousing is not meant for current, "live" data.
Data Marts:
Data warehouses can become enormous with hundreds of gigabytes of transactions. As a result, subsets, known as "data marts," are often created for just one department or product line.
ETL:
Data Warehouse acquisition processes of Extracting, Transforming (or Transporting) and Loading (ETL) data from source systems into the data warehouse.
www.orafaq.com/glossary/faqglose.htm
Three database functions that are combined into one tool to pull data out of source databases and place it into target databases. ETL is used to migrate data from databases to others, to form data marts and data warehouses and also to convert databases from one format or type to another.
