Saturday, September 5, 2015

SSAS: Storage Modes

As we know cubes pulls the data from relation database and stores it in cube. Storage mode helps cube to store data in cube and dimension.
There are three storage modes available in SSAS
                                  - MOLAP
                                  - ROLAP
                                  - HOLAP

MOLAP or multi dimensional Online Analytical Processing is the default storage mode of SSAS cube. MOLAP takes the copy of facts and dimensions. ROLAP leaves the fact and dimension data in relational tables. HOLAP use both relational as well as multi dimensional storage, mostly aggreations stores in MOLAP and fact and dimensions store in ROLAP.

Important note is dimension can have options to use either MOLAP or ROLAP unlike cubes where all the 3 storage mode is suitable.

Now we can look at the advantage and disadvantage of these storage modes which helps us to choose the proper storage mode based on the requirement.