Rtolap
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[edit] RTOLAP - Real Time OLAP
Whilst many OLAP Servers such as Microsoft Analysis Services store pre-calculating consolidations and calculated elements to achieve rapid response times a Real Time OLAP Server will calculate the values on the fly, when they are required. The essential characteristic of RTOLAP system is that it holds all the data in RAM.
[edit] Advantages
- Since precalculated values aren't stored the size of a cube in an RTOLAP system will be smaller than that of an OLAP product which resorts to precalculation. RTOLAP often reduced the problem which may be associated with "Data explosion" since less data is stored.
- RTOLAP essentially performs calculations "just-in-time" by only calculating values when they are needed space can be saved, since in a precalculated system, a great deal of calculations will be stored which may well never be called up.
- Incremental updates are available as soon as they are loaded, and any modifications to data will flow through the system immediately. With RTOLAP when a change is made, everyone sees the result. This isn't a unique characteristic of RTOLAP, since other OLAP systems (e.g. Microsoft Analysis Services, MicroStrategy) behave the same way.
[edit] Disadvantages
- Since RTOLAP stores the entire cube in RAM, it doesn't scale to the data volumes larger then the RAM size
- Performance of queries can be slower since the values need to be calculated on the fly instead of being accessed from the precalculated storage
