Notes11 - Warehousing Data Warehousing Overview CS245 Notes...

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1 Data Warehousing Overview CS245 Notes 11 Hector Garcia-Molina Stanford University CS 245 1 Notes11 Warehousing Growing industry: $8 billion in 1998 Range from desktop to huge: Walmart: 900-CPU, 2,700 disk, 23TB Teradata system CS 245 Notes11 2 Lots of buzzwords, hype slice & dice, rollup, MOLAP, pivot, . .. Outline What is a data warehouse? Why a warehouse? Models & operations CS 245 Notes11 3 Implementing a warehouse Future directions What is a Warehouse? Collection of diverse data subject oriented aimed at executive, decision maker often a copy of operational data CS 245 Notes11 4 with value-added data (e.g., summaries, history) integrated time-varying non-volatile more What is a Warehouse? Collection of tools gathering data cleansing, integrating, . .. querying reporting analysis CS 245 Notes11 5 querying, reporting, analysis data mining monitoring, administering warehouse Warehouse Architecture Client Client Query & Analysis CS 245 Notes11 6 Warehouse Source Source Source Integration Metadata
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2 Motivating Examples Forecasting Comparing performance of units Monitoring, detecting fraud CS 245 Notes11 7 Visualization Why a Warehouse? Two Approaches: Query-Driven (Lazy) Warehouse (Eager) CS 245 Notes11 8 Source Source ? Query-Driven Approach Client Client Mediato CS 245 Notes11 9 Wrapper Wrapper Wrapper Mediator Source Source Source Advantages of Warehousing High query performance Queries not visible outside warehouse Local processing at sources unaffected CS 245 Notes11 10 Can operate when sources unavailable Can query data not stored in a DBMS Extra information at warehouse Modify, summarize (store aggregates) Add historical information Advantages of Query-Driven No need to copy data less storage no need to purchase data M t dt dt CS 245 Notes11 11 More up-to-date data Query needs can be unknown Only query interface needed at sources May be less draining on sources OLTP vs. OLAP OLTP: On Line Transaction Processing Describes processing at operational sites OLAP: On Line Analytical Processing Describes processing at warehouse CS 245 Notes11 12
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3 OLTP vs. OLAP Mostly updates Many small transactions Mb-Tb of data Mostly reads Queries long, complex Gb-Tb of data OLTP OLAP CS 245 Notes11 13 Raw data Clerical users Up-to-date data Consistency, recoverability critical Summarized, consolidated data Decision-makers, analysts as users Data Marts Smaller warehouses Spans part of organization e.g., marketing (customers, products, sales) CS 245 Notes11 14 Do not require enterprise-wide consensus but long term integration problems?
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Notes11 - Warehousing Data Warehousing Overview CS245 Notes...

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