what is olap in data warehouse and types of olap

             what is olap in data warehouse and types of olap

In this tutorial learn what is olap in data warehouse and types of olap previous tutorial what is metadata repository in data warehouse

OLAP(Online analytical processing):

 OLAP is an approach to answering multi-dimensional analytical (MDA) queries swiftly OLAP is part of the broader category of business intelligence, which also encompasses relational database, report writing and data mining.

OLAP tools enable users to analyze multidimensional data interactively from multiple perspectives.

OLAP consists of three basic analytical operations:

Consolidation (Roll-Up)

Drill-Down

Slicing And Dining

consolidation devolve the predation of data that can be accurate and tried one or more dimensions, for example, all sales sheet are rolled op to the wie department or sales division to anticipate sales trends

The dull down is a technique that allows users to navigate that the details, for instance, users can view the sales by an individual product that make up remain Sale

Slicing and dicing is a feature whereby users can take out (allein specified wat of the OLAP cube and view (diene) the slices from different viewpoints

Types of OLAP:

1. Relational OLAP(ROLAP):

• ROLAP works directly with relational databases. The base data and the dimension tables are stored as relational tables and new tables are created to hold the segregated information.

It depends on a specialized schema design This methodology relies on manipulating the data stored in the relational database to give 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 SOL statement ROLAP tools do not use pre-calculated data cubes but instead pose the query to the standard relational database and its tables in order to bring back the data required to answer the question ROLAP tools feature the ability to ask any question because the methodology does not limit to the contents of a cube, ROLAP also has the ability to drill down to the lowest level of detail in the database.

2. Multidimensional OLAP (MOLAP):

MOLAP is the 'classic' form of OLAP and is sometimes referred to as just OLAP.

MOLAP stores this data in optimized multi-dimensional array storage, rather than in a relational database. Therefore it requires the pre-computation and storage of information in the cube - the operation known as processing.

• MOLAP tools generally utilize a pre-calculated data set referred to as a data cube. The data cube contains all the possible answers to a given range of questions.

• MOLAP tools have a very fast response time and the ability to quickly write back data into the data set.

3. Hybrid OLAP(HOLAP):

• There is no clear agreement across the industry as to what constitutes Hybrid OLAP, except that a database will divide data between relational and specialized storage.

   For example, for some vendors, a HOLAP the database will use relational tables to hold the larger quantities of detailed data, and use specialized storage for at least some aspects of the smaller quantities of more-aggregate or less-detailed data.

  HOLAP addresses the shortcomings of MOLAP and ROLAP by combining the capabilities of both approaches.

 • HOLAP tools can utilize both pre-calculated cubes and relational data sources