Differences between ROLAP and molap

1. In terms of storage methods, front-end modeling is a multi-dimensional approach, while ROLAP is stored in relational databases, while molap is stored in a unique file mode, you can use either of the following methods for typical operations, such as corner stone.
2.
The molap storage mode enables partition aggregation and copies of its source data to be stored on the Analysis Server computer in a multidimensional structure.
The ROLAP storage mode enables the partition aggregation to be stored in the tables of the relational database (specified in the partition data source.
Unlike the molap storage mode, ROLAP does not store copies of source data. When the results cannot be derived from aggregation or client cache, the fact data table of the partition is accessed to answer the query. In the ROLAP storage mode, query response is generally slower than in the other two storage modes. ROLAP is usually used for large datasets that are not frequently queried, such as historical data older than the year.
3.
ROLAP and molap are storage methods:


Partitioned Storage
The physical storage option affects the performance, storage requirements, and storage location of the partition and its parent cube. One option is the partition storage mode. A partition can have one of the following three storage modes:

Multi-dimensional OLAP (molap)


Relational OLAP (ROLAP)


Hybrid OLAP (holap)
Microsoft & reg; SQL Server 2000 Analysis Services supports all three storage modes. In the Application storage design wizard, you can select the storage mode that is most suitable for partitioning. Alternatively, you can use the use-Based Optimization Wizard to select a storage mode based on the query that has been sent to the cube and optimize the aggregation design. When three storage modes are used, you can also use explicit filtering to restrict the source data read into the partition.

When molap and ROLAP storage modes are used for dimensions and local cubes instead of partitions, their meanings are different. The holap storage mode cannot be used for dimensions or local cubes.

Molap
The molap storage mode enables partition aggregation and copies of its source data to be stored on the Analysis Server computer in a multidimensional structure. Whether a partition is a local partition or a remote partition, the computer can be an analysis server computer that defines the partition, or another Analysis Server computer. The multi-dimensional structure used to store partition data is located in the subfolders of the data folder on the Analysis Server. For more information about the data folder, see Analysis Server.

Because the analysis server computer resident a copy of the source data, even if the query results cannot be obtained from the partition aggregation, you can solve the query without accessing the source data of the partition. Based on the percentage and Design of partition aggregation, The molap storage mode provides the potential to achieve the fastest query response time. All in all, molap is more suitable for partitioning in frequently used cubes and for quick query response.

ROLAP
The ROLAP storage mode enables the partition aggregation to be stored in the tables of the relational database (specified in the partition data source. However, you can use the ROLAP storage mode for partition data, instead of creating an aggregation in a relational database. For more information, see set aggregation options (storage design wizard) or set aggregation options (based on the use of the Optimization Wizard ).

Similarly, if the partition source data is stored in SQL Server 2000 and the specified conditions are met, the index view is created instead of the table. For more information, see the ROLAP partition index view.

Unlike the molap storage mode, ROLAP does not store copies of source data. When the results cannot be derived from aggregation or client cache, the fact data table of the partition is accessed to answer the query. In the ROLAP storage mode, query response is generally slower than in the other two storage modes. ROLAP is usually used for large datasets that are not frequently queried, such as historical data older than the year.



If the data source is analysis services Program Is a Microsoft ole db provider for analysis services), you cannot create an aggregation for partitions in the ROLAP storage mode.


Holap
The holap storage mode combines the features of molap and ROLAP. Like molap, holap stores partition aggregation in a multidimensional structure on the Analysis Server computer. Holap does not store copies of source data. For queries that only access the summary data contained in partition aggregation, holap and molap features the same. To query the source data (for example, to deepen the process to an atomic multi-dimensional dataset unit, but this unit does not have the corresponding aggregated data), You must retrieve the data from the relational database, it will not be as fast as the source data is stored in the molap structure.

Partitions stored by holap are smaller than those stored by molap, which is faster than query involving summary data. In general, the holap storage mode is applicable to partitions in a multi-dimensional dataset that requires rapid query and response based on a large amount of source data.