In this paper, the Online Analytical Processing system (OLAP) and its logical models have been discussed. By the use of OLAP operations, data analysis is done which can be used to help the user or the person in decision making. The modern data warehouses store or accumulate a large amount of data to perform computations. Here, OLAP operations are used for the computation of complex sub queries in the data warehouse. Decision support systems depend on multidimensional modeling. Therefore, by using OLAP (Online Analytical Processing), decision makers can analyze the data and can arrive at a point where the highest probability of the decision taken will result in success. Data at different aggregation levels, are analyzed using OLAP operators such as roll-up and drilldown. Roll-up operators decrease the details of the measure, aggregating it along the dimension hierarchy and drill-down operators increase the details of the measure.

Keywords : OLAP, data warehousing, logical models