OLAP Model:

There are four OLAP Models

1) MOLAP,

2) ROLAP

3) HOLAP

4) DOLAP

1) MOLAP: This is the more traditional way of OLAP analysis. In MOLAP, data is stored in a multidimensional cube. The storage is not in the relational database, but in proprietary formats.

2) ROLAP:

This methodology relies on manipulating the data stored in the relational database to the the appearance of traditional OLAP's slicing and dicing functionality. In essence, each action of slicing and dicing is equivalent to adding a "WHERE" clause in the SQL statement.

3) HOLAP:

• HOLAP technologies attempt to combine the advantages of MOLAP and ROLAP. For gummary-type information, HOLAP leverages cube technology for faster performance.
• When detail information is needed, HOLAP can "drill through" from the cube into ane underlying relational data.
• For example, a HOLAP server may allow large volumes of detail data to be stored in a relational database, while aggregations are kept in a separate MOLAP store. The Microsoft SQL Server 7.0 OLAP Services supports a hybrid OLAP server.

4) DOLAP:

It is Desktop Online Analytical Processing and variation of ROLAP. It offers portability to users of OLAP. For DOLAP, it needs only DOLAP software to be present on machine.Though this software, multidimensional data-sets are formed and transferred to desktop machine.