Online Analytical Processing (OLAP)
Online Analytical Processing (OLAP) is a technology by which Data Warehouse data are queried and analysed.A Data Warehouse is the repository that stores large amount of data extracted from a variety of source systems exist within the organisation. A Data Warehouse does not necessarily need OLAP technology. OLAP enables users to gain insight into data. OLAP uses a multidimensional view of aggregate data to provide quick access to strategic
information for analysis purposes.
OLAP lowers the incidence of erroneous interpretations, reducing the amount of data "noise",eases navigation of the database, screening for a particular subset of data, asking for the data in a particular orientation and defining analytical calculations.
The key concepts in OLAP are:
Measure or Fact
It is a data variable that stores business information, classified by one or more mutually independent categorising structures.
a logical grouping of dimension values sharing the same level of abstraction within a hierarchy.
is a categorising structure by which business measures are classified for analysis purposes
Consists of many dimension values each
representing a distinct category of
When a measure is
classified by a number of dimensions, we
say that the measure is dimensioned by
It is a parentage structure by which dimension values are organised.
Parent and Child
The dimension values,
dimension values are related to each other
as parents, children or siblings ,Once grouped into
levels and hierarchies.
single data-point that
occurs at the intersection defined by
selecting one dimension value from each
dimension in the measureâ„¢s
collective term for the
multi-dimensional array of data cells.
Drill Up, Drill Down
a specific analytical technique
whereby the user navigates among
dimension levels, from the most
summarized to the most detailed.
Many a times, there is a requirement to dig deeper for more
detailed information that are not in the cube.This is achieved by a drill
through operation from the cube into relational Data Warehouse data.
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