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© 2009 Wipro Ltd – Internal & Restricted
Advanced OLAP ConceptsAdvanced OLAP ConceptsPart 2Part 2
<OLAP Concepts 201 Series>Renu Singh
© 2009 Wipro Ltd - Confidential2 © 2009 Wipro Ltd - Confidential2
OLAP Overview• On-Line Analytical Processing is a decision support
software that allows the user to quickly analyze information that has been summarized into multidimensional views and hierarchies.
• There are three main features of OLAP system : Multidimensional Viewing – OLAP supports
multidimensional model which consists of facts and dimensions also called as Star Schema.
Calculation Intensive Capabilities – Due to data is stored in facts and dimensions tables, it enables users to analyze data without much calculations.
Time Series analysis – Enables users to analyze data across time.
• This Module will cover the details in four parts:– Part 1 – OLAP Modeling – Building Blocks– Part 2 – OLAP Types & Architectures – Part 3 – OLAP Reporting Styles – Part 4 – OLAP Issues & Optimization
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OLAP Objectives
Upon completion of this module you will be able to:• Various OLAP Types and their Architectures
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OLAP Outline
Lesson 1 OLAP Types and Architectures
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OLAP Types & Architectures
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Data is stored in multidimensional cubes MDDB technology is proprietary. Compilation intensive architecture. Load involves series of aggregations across orthogonal
dimensions Good to access pre-aggregated data
MOLAP – Multidimensional OLAP
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Advantages• Intuitive• Performance
advantages• Ease of navigation• Little Performance
Tuning required
MDDB - A perspective
Disadvantages• Proprietary• No standard storage
techniques• Aggregate explosion
problem• Limited to 50-100 GB of
calculated data
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Store atomic data in a proprietary data structure (MDDB), pre-calculate as many outcomes as possible, obtain OLAP functionality via proprietary algorithms running against this data.
Obtain multi-dimensional reports from the DSS Client
MOLAP - Architecture
MDDB Engine MDDB Engine Decision Support Client
Database Layer Application Logic Layer Presentation Layer
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Support for large databases with good performance Excellent platform portability Good exploitation of hardware advances such as parallel
processing Codd rules however are not concerned about storage, but
about functionality only
ROLAP
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Advantages • Robust security • Multi-user concurrent access
(e.g. read-write with locking) • Widely recognized standards • Openness to multiple tools • Based on familiar, proven
and scalable technology Extraction & Replication Parallelization Query Optimization Advanced Indexing
techniques
ROLAP - A Perspective
Disadvantages• Computation Intensive
queries are slow.• Additional layer of OLAP
engine• Non intuitive
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Three tiered Architecture : • OLAP interface • ROLAP engine• RDBMS
ROLAP - Architecture
Data Warehouse ROLAP Engine Decision Support Client
Database Layer Application Logic Layer Presentation Layer
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Hybrid approach seeks to provide best of both worlds - MOLAP and ROLAP
Create MDB structures for fast analytical needs Create mappings to RDBMS for larger data volumes The engine hides these mappings/ structures from the end
user
HOLAP - Hybrid OLAP
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Advantages• Performance due to MDB
structures• Integration with data
maintained in RDBMS• Leverages RDBMS engine
and administration skills• Support for large volumes of
data by Relational Mappings
Hybrid OLAP - A perspective
Disadvantages• Managing large number of
data structures• Complex Architecture• Expensive
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HOLAP - Architecture
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Desktop OLAP tools work by extracting RDBMS data into local (or server) MD cubes
User queries are limited to the predefined dimensions in the hypercube
Do not provide shared environment Do not provide read/write capabilities Low cost tools
DOLAP
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DOLAP - Architecture
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Most OLAP products can now be deployed to Web browsers Approaches used
• Static Web publishing - The reports are generated in the form of HTML documents
• Using a Web OLAP Server - Simple scripts allow users to perform basic manipulations like dimension rotations, drill downs and dimension member selections
Web OLAP
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Web OLAP - Architecture
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Congratulations! You have now completed the module OLAP Types
You should now be able – Understand different OLAP Types– Architecture– Advantages Disadvantages
Module Summary
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Quiz
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The cube structure in OLAP achieves the __________functionalitya) Sharedb) Informationc) Collectiond) Multidimensional
Question 1
Answer: D
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Aggregation provides OLAP with __________
a) Multidimensional Datab) Pre Calculated Datac) Slow Retrievald) Nested Data
Question 2
Answer: B
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MDDB Engine is used in __________architecturea) HOLAPb) WOLAPc) MOLAPd) None of the above
Question 3
Answer: C
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Deploying OLAP products on Web Browsers is
a) Web Deploymentb) WOLAPc) Web Reportsd) None of the above
Question 4
Answer: B
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ROLAP Architecture includes
a) DBMS, Engine, DSSb) DBMS, ROLAP Engine, OLAP Interfacec) ROLAP Engined) None of the above
Question 5
Answer: B
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References
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References
Library:Tek-tips reporting solutions
forumhttp://www.dmreview.com/http://www.dwinfocenter.org
Data warehouse and OLAP – Concepts, Architecture and Solutions by Robert Wrember & Christian Koncilia
The OLAP Report by Nigel Pendse and Richard Creeth
The OLAP Solutions – Building Multidimensional Information Systems Second Edition by Erik Thomsen, Wiley dreamtech India Pvt. Ltd. 2002 ISBN 81-265-0275-4
Publications Publications
Training ProgramsURL’s