Design Issues When and how to gather data Source driven architecture:data sources transmit new information to warehouse,either continuously or periodically (e.g.,at night) Destination driven architecture:warehouse periodically requests new information from data sources Keeping warehouse exactly synchronized with data sources (e.g.,using two-phase commit)is too expensive Usually OK to have slightly out-of-date data at warehouse Data/updates are periodically downloaded form online transaction processing (OLTP)systems. What schema to use Schema integration Database System Concepts-6th Edition 20.7 @Silberschatz,Korth and SudarshanDatabase System Concepts - 6 20.7 ©Silberschatz, Korth and Sudarshan th Edition Design Issues When and how to gather data Source driven architecture: data sources transmit new information to warehouse, either continuously or periodically (e.g., at night) Destination driven architecture: warehouse periodically requests new information from data sources Keeping warehouse exactly synchronized with data sources (e.g., using two-phase commit) is too expensive  Usually OK to have slightly out-of-date data at warehouse  Data/updates are periodically downloaded form online transaction processing (OLTP) systems. What schema to use Schema integration