MOLAP is the term used to refer to multidimensional online analytical processing. It extends traditional OLAP processing through indexing directly into a multidimensional database. This allows users to view various data aggregates in different manners without the added overhead required to conduct similar operations with a relational database.
Advantages and Disadvantages of MOLAP
Some of the advantages of using MOLAP include the ability to perform complex calculations in a fast manner. This is due to all potential calculations being pre-completed with the MOLAP cube is generated returning results in a linear or fast response time. The overall performance for MOLAP data cubes is also significantly faster than other data storage options and is preferred for data slicing operations. Disadvantages of MOLAP include that it is limited in the data types that it can store. Since MOLAP cubes conduct all possible calculations during cube creation, but the type and amount of data stored can become limited. MOLAP also costs additional money to implement since the majority of implementations are considered proprietary and would run an up-front cost for an organization to adopt the technology.
Advantages and Disadvantages of ROLAP
ROLAP stands for relational online analytical processing and relies on manipulation of data stored in a relational database to make it look like it has the traditional OLAP slice and dice functionality. These actions are considered to be the equivalent of a “WHERE” SQL clause. Some advantages of ROLAP include the ability to handle a large amount of data with only the relational database providing any constraints on the database size. ROLAP can also make use of already created functionalities found in the database without additional work to incorporate. ROLAP is significantly slower than MOLAP, however, because of having to parse the equivalent of a SQL query to conduct data base operations. The larger the data set, the slower ROLAP queries will take to execute. ROLAP can also be limited by its reliance on SQL functions, requiring many operations to be build on-top of those pre-existing to conduct desired operations.
Advantages and Disadvantages of HOLAP
HOLAP stands for Hybrid Online Analytical Processing and attempts to combine the best parts of ROLAP and MOLAP in order to provide the fastest performance over the largest data set possible. HOLAP lets some of the data store be defined in a MOLAP cube and other information in ROLAP depending on the nature of the design of the product. Typically, HOLAP implementations will store time-based information in the MOLAP cube, and conditions-based or older information in the ROLAP data store. Disadvantages of HOLAP include greater up-front cost and the complexity of the database implementation potentially driving up maintenance costs for businesses or organizations implementing the technology.