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DW Components Data migration tools –Tools that help extract, transform and load data into the data warehouse –Three main categories Data copying and replication Data transformation Data cleansing Metadata usage –Administrative and end-user
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Two-Tier DW Architecture
ExternalData Sources
Desk-TopReporting & Analysis
Tools
DataWarehouse
ERP Systems(Operational Systems)
Other InternalData Sources
Three-Tier DW Architecture
OperationalDB
OperationalDB
Externaldata
DataWarehouse
End-Users
CustomerData Mart
ProductData Mart
ProductionData Mart
DW Components
• Data migration tools– Tools that help extract, transform and load data into
the data warehouse– Three main categories
• Data copying and replication• Data transformation• Data cleansing
• Metadata usage– Administrative and end-user
DW Components • Warehouse data stores
– Structures used to actually store the data– Typically relational DB (but not always)– Multi-dimensional DB becoming more popular
• Data retrieval, formatting and analysis– Query tools– Analysis tools– Data mining
• Management tools– Access control, performance monitoring, usage
monitoring
Steps in Data Warehousing
1. Identify all the sources of data2. Design the data warehouse3. Extract/Transform/Load process4. Decision making from DW
DW Design: Star SchemaLots of records, but each record is “thin”
Fewer records, but each record is “fat” (lots of big columns)
Want to be able to “see” each Sale by
Product,Time, Store
“Fact”
“Dimensions”
E/T/L Process• Extract
– Data must be extracted from source systems• Transform
– Cleansing• Identify and eliminate data inconsistencies• Can be very complex, expensive, time consuming
– Aggregation• Load
– Must be repeated periodically– How often? – Identifying changed data
DW Process Overview
DataWarehouse
Operational Systems
Other InternalData Sources
Extract/Transform/Load
External DataSources
Query, Reporting& Analysis
Tools
PeriodicUpdates
PeriodicUpdates
PeriodicUpdates
PeriodicUpdates
