What is MOLAP?

MOLAP, or multidimensional Online Analytical Processing, is one of the technologies used in OLAP servers, and is an alternative to ROLAP. Although both MOLAP and ROLAP analytic tools facilitate analysis of data via the usage of a multidimensional data model, MOLAP's point of difference comes with the fact that it requires pre-computation and storage of information in the cube (explained in the previous post), which is certainly an effort in the initial stages, but one that pays off handsomely later on. Following are some of the benefits of MOLAP over ROLAP:

• MOLAP cubes allow extremely quick data retrieval due to multidimensional indexing and caching, as well as optimized storage. They are also perfect for slicing and dicing operations.
• They are capable of complex calculations, since all of the same have been pre-generated during the creation of the cube. Also, while there is a certain disadvantage in the fact that the cube once created can't hold any more data, this does not mean that it can't store tremendous amounts of data. Hence, with a bit of future planning, MOLAP can serve the organization's interests quite well.
• There is a smaller amount of on-disk data as compared to ROLAP since there are some pretty advanced compression techniques used in MOLAP.
• There is automatic computation of higher level aggregates of data.
• Array models facilitate natural indexing.

So as you can see, there are actually many reasons why companies prefer MOLAP over ROLAP as the technology for their OLAP server.