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Relational OLAP and Aggregate Navigators. Data Warehousing Lab. M.S. 2 Hyeyoung Cho. OLAP. OLAP(OnLine Analytical Processing) One technology for querying the warehouse Suited for summarizing and analyzing huge quantities of data 4 basic functions Multidimensionality Drill down

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Relational olap and aggregate navigators

Relational OLAP and Aggregate Navigators

Data Warehousing Lab.

M.S. 2 Hyeyoung Cho


  • OLAP(OnLine Analytical Processing)

    • One technology for querying the warehouse

    • Suited for summarizing and analyzing huge quantities of data

    • 4 basic functions

      • Multidimensionality

      • Drill down

      • Rotation

      • Multiple modes of view

Olap basic functions
OLAP basic functions

  • Multidimensionality

    • provide data about performance measures, broken down by one or more dimensions

    • dimensions

      • combine to describe measures

      • vary according to industry, strategy, kinds of information that systems capture

    • filtered by dimension and/or measure value

Olap basic functions2
OLAP basic functions

  • Drill down

    • break a summary item into its detailed components

    • multiple parallel hierarchies

      • DATE dimension(year vs. seasonal year)

both share a

common atomic

data element : day

Olap basic functions3
OLAP basic functions

  • view highly summarized data and then navigate down to less summarized data

  • drill across:drill down into a different dimension

  • rolling up:drill from a detail back up to a total

Olap basic functions4
OLAP basic functions

  • Rotation

month on the Y-axis

product on the X-axis


month on the X-axis

product on the Y-axis

Olap basic functions5
OLAP basic functions

  • change view perspective

  • drill down and rotation

Olap basic functions6
OLAP basic functions

  • Multiple modes of view

    • View data in a variety of formats(graph,chart,etc.)

Olap database technologies
OLAP database technologies

  • OLAP

    • application for querying and viewing data

    • regardless of how that data is stored


    • ROLAP (Relational OLAP) :RDB기반

    • MOLAP (Multidimensional OLAP) :MDDB기반

  • data marts

    • tuned for specific subject areas

    • more normalized than simple star schema

Olap database technologies1
OLAP database technologies

  • Cube(dataset to analyze)

    • three dimension : height,width,depth(dice)

    • Comprised of any number of dimensions


  • Array

    • RDB : store data in tables and columns

    • MDDB : store data in large multidimensional arrays

  • Multidimensional Database Vendors

    • Oracle Express Server(OES)

    • Essbase(Hyperion Software)

    • Powerplay(Cognos)

    • Gentia(Gentia Software)

  • Suitable for analyzing narrowly focused sets of data


  • Aggregate Navigation

    • Oracle 8i ’s query rewrite capabilities

    • Materialized views in Oracle 8i

      • ease the construction and maintenance of the table

      • speed up query performance


  • aggregate navigators

    • select the best table for each query

    • know which summaries exist and the size


  • ROLAP Vs. Online Report Writing

    • support

      • Generate SQL calls, Format the results

    • not support

      • OLAP basic function, Aggregate navigation

  • ROLAP tool vendors

    • Oracle Discoverer

    • MicroStrategy DSS Agent,

    • Computer Associates DecisionBase

Rolap vs molap

  • query performance

    • query response time

    • precalculate all combinations and summaries of data

      • three dimensions:

        • 1개의 3D atomic level array

        • 3개의 2D atomic level array

        • 3개의 1D summary array broken by each dimension

Rolap vs molap2

  • load performance

    • populate data structures and perform calculations time

Rolap vs molap3

  • Analytic capability

Rolap vs molap4

  • Dataset Sizes

  • Dimension Handling

Rolap vs molap5

  • Maintenance Effort

Rolap and molap harmony
ROLAP and MOLAP Harmony

  • Which technology wins?

    • relational database : a large, cross-functional, enterprise data warehouse

    • multidimensional database : a well-defined, highly targeted analysis-focused data mart limited dimensionality and little need for detailed, atomic-level data

  • A corporate data warehouse feeds smaller, narrowly focused or stand alone data marts

    → ROLAP and MOLAP are complementary!

Rolap and molap harmony1
ROLAP and MOLAP Harmony

  • drill through

    • integrate ROLAP and MOLAP technologies

      • drill down in the MDDB until reach in the lowest level of detail

      • query to RDB that contains very detailed atomic-level data

      • not perfect yet so require the custom code each drill-through query


  • OLAP is a user interface, not a data storage, concept

  • OLAP basic functions: multidimensionality, Drill down, Rotation, Multiple modes of view


  • What is a best approach to OLAP?