HOLAP (Hybrid Online Analytical Processing) is a combination of ROLAP and MOLAP which are other possible implementations of OLAP. HOLAP allows storing part of the data in a MOLAP store and another part of the data in a ROLAP store. The degree of control that the cube designer has over this partitioning varies from product to product.
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Vertical partitioning
In this mode HOLAP stores aggregations in MOLAP for fast query performance, and detailed data in ROLAP to optimize time of cube processing.
Horizontal partitioning
In this mode HOLAP stores some slice of data, usually the more recent one (i.e. sliced by Time dimension) in MOLAP for fast query performance, and older data in ROLAP. Moreover, we can store some dices in MOLAP and others in ROLAP, leveraging the fact that in a large cuboid, there will be dense and sparse subregions [1].
Products
Examples of commercial products which support HOLAP storage mode are Microsoft Analysis Services, MicroStrategy and SAP AG BI Accelerator.
Footnotes
- ^ Owen Kaser and Daniel Lemire, Attribute Value Reordering for Efficient Hybrid OLAP, Information Sciences, Volume 176, Issue 16, pages 2279-2438, 2006.
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