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 Synchronous vs asynchronous replication Keeping warehouse exactly synchronized with data sources(e.g., using two-phase commit)is often too expensive Usually OK to have slightly out-of-date data at warehouse -Data/updates are periodically downloaded form online transaction processing (OLTP)systems.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-7th Edition 11.10 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 11.10 ©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 • Synchronous vs asynchronous replication ▪ Keeping warehouse exactly synchronized with data sources (e.g., using two-phase commit) is often too expensive ▪ Usually OK to have slightly out-of-date data at warehouse ▪ Data/updates are periodically downloaded form online transaction processing (OLTP) systems.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