There are three different types of OLAP technology:
ROLAP stands for Relational-OLAP as it stores all the data in relational database. When we run the MDX queries it retrieves the data from the relational database using a corresponding SQL query. This makes the query processing to be slow but it does provide faster processing time.
MOLAP stands for Multidimensional-OLAP as it stores all the data in the multidimensional data structure of the Analysis Services. It has slow processing time but provides better query performance than ROLAP. MOLAP storage mode is most widely used as OLAP is meant to provide the faster query performance.
HOLAP stands for Hybrid-OLAP as it uses a combination of both the ROLAP and MOLAP. It stores only the indexes and aggregations in the multidimensional form while the rest of the data is stored in the relational database.
