MOLAP

General information

The described system is most evident and easy to use as it allows to reflect and consider any interrelations in the most complex multicomponent systems. Detailed and aggregated data contain in multidimensional base. Data storage in multidimensional structures allows to manipulate data as a multidimensional array thanks to what the speed of calculation of modular values is identical to any of measurements. MOLAP assumes creation of the explicit, physically stored multidimensional cube (or several cubes) with accomplishment of analytical requests only over them, without the appeal to a relational DB. In this case the largest performance is reached, however in this case the multidimensional database is excessive as multidimensional data completely contain detailed relational data.

Application conditions

Proceeding from everything, considered earlier, use of the MOLAP system is reasonable only under following conditions:

• the small volume of initial data for the analysis (no more than several gigabytes), i.e. the level of aggregation of data is rather high
• a set of information measurements is stable (as any change of their structure almost always requires complete reorganization of a hyper cube)
• time of the answer of a system for independent requests is the most important parameter

Typical circuit of implementation of MOLAP

Quality evaluation of MOLAP

Practical use of the multidimensional OLAP systems allowed to draw conclusions on their merits and demerits in comparison with the relational systems.

Advantages of MOLAP

• high performance. Search and data sampling are made much quicker, than in relational databases
• the structure and interfaces in the best way correspond to structure of analytical requests
• multidimensional DBMS easily cope with integration into an information model of various additional functions

Shortcomings of MOLAP

• MOLAP can work only with own multidimensional DB and are based on patent license solutions for multidimensional DBMS that affects the price. Such technologies provide a full stroke of OLAP processing and or include, in addition to the server module, own integrated client interface, or use for communication with the user external programs of work with spreadsheets
• low performance indicators of use of an external bulk memory, the worst, in comparison with relational, a DB transaction mechanisms
• There are no uniform standards on the interface, languages of the description and data management
• Do not support the replication of data which is often used as the loading mechanism

Literature

• Labotsky V.  V.  Knowledge management: technologies, methods and means of representation, extraction and measurement of knowledge  — Minsk: BGEU, 2006
• Alperovich M. Technologies of storage and processing of corporate data (Data Warehousing, OLAP, Data Mining)
• Shchavelev L.  V.  Methods of analytical data processing for decision support.  — Open systems,  No. 4-5, 1998

Links

• Internet university of high technologies
• SIT-forum
• Knowledge Management