Online Analytical Processing (OLAP) is an efficient tool for the analytical processing of multidimensionally prepared, very large data volumes, which can originate from data marts, from the Data Warehouse( DWH) or even from operational systems. OLAP, which is closely related to data warehousing, structures data in a hierarchical manner and usually allows both individual and trend analyses, enabling managers and analysts to obtain decision-relevant information quickly and easily. Interactive access to the data material enables different perspectives on company information and a representation of the company that is as close to reality as possible.
The data can be prepared statically or dynamically, i.e. immediately or online. By means of the OLAP tools the presentation of the data on screen, paper, browser etc. in the form of tables, lists or graphics is supported.
Thus, OLAP tools are used for presentation and are characterized by fast, interactive reactions. They are suitable for the analysis of data, which must be presented in temporal relations, as well as for the presentation of deviations and exceeding of tolerance limits. The best known OLAP presentation and analysis tool is the multidimensional OLAP cube.
There are several OLAP variants: Desktop OLAP( DOLAP) where the OLAP data is not stored on the server side, but directly on the desktop. Hybrid OLAP( HOLAP) with the hybrid storage of the detailed data in a relational database and the aggregation data on the OLAP cube. Multidimensional OLAP( MOLAP) with the multidimensional storage of the detail and aggregation data and RelationalOLAP ( ROLAP) where the detail and aggregation data are stored in a relational database. Some of the mentioned OLAP variants are the combination of two OLAP techniques.