Heterogeneous Distributed Data base 研究生课《高级数据库系统技术》 Environment Global User Local user ocal User Global Distributed Schema DBMS DBMS-1 DBMS-2 DBMS-3 DBMS-n 重庆邮电大学空间信息系统研究所
研究生课《高级数据库系统技术》 重庆邮电大学·空间信息系统研究所 21 Heterogeneous Distributed Database Environment
Distributed dbms architecture/研究生课《高级数据库系统技术》 Distributed Distributed/ data pository repository Distributed Distributed DBMS DBMS Application Communications Communications Application programs controller controller programs User terminals DBMS DBMS terminals Database Database site 1 site n 22 重庆邮电大学空间信息系统研究所
研究生课《高级数据库系统技术》 重庆邮电大学·空间信息系统研究所 22 Distributed DBMS Architecture
Comparison of distributed dB Design Strategies 研究生课《高级数据库系统技术》 Strategy Reliability Expanda Communications Overhead Manageability Data consistenc Centralized POoR: POOR VERY HIGH: VERY GOOD: EXCELLENT Highly dependent Limitations are High traffic to one site One, monolithic site All users always have on central server barriers to es little same data performance coordination Replicated GOOD VERY GOOD LOW to MEDIUM: VERY GOOD MEDIUM Redundancy and Cost of additional Not constant, but Each copy is like Fine as long as delays snapshots tolerated delays copies may be less periodic snapshots every other one are tolerated by than linear can cause bursts of business needs network traffic Synchronized EXCELLENT: VERY GOOD MEDIU MEDIUM MEDIUM to replication Redundancy Cost of additional Messages are Collisions add VERY GOOD and minimal copies may be low constant but some some complexity Close to precise delays and synchronization delays are tolerated to manageability consIstency work only linear Integrated VERY GOOD: VERY GOOD: LOW to MEDIUM: DIFFICULT: VERY POOR partitions Effective use of New nodes get only Most queries are local Especially difficult for Considerable effort partitioning and data they need but queries which queries that need data and inconsistencies without changes in require data from from distributed not tolerated overall database multiple sites can tables, and updates cause a temporary must be tightly coordinated Decentralized GOOD GOOD LOW: VERY GOOD: LOW: ith Depends on only New sites ittle if any need to Easy for each site. No guarantees of independent local database dependent of pass data or queries until there is a need to consistency, in fact partitions availability existing ones across the network share data across pretty sure of (if one exists inconsistency 23 重庆邮电大学空间信息系统研究所
研究生课《高级数据库系统技术》 重庆邮电大学·空间信息系统研究所 23 Comparison of Distributed DB Design Strategies
Client/server Database Systems TheSimple" Case of Distributed Database Systems?
研究生课《高级数据库系统技术》 重庆邮电大学·空间信息系统研究所 Client/Server Database Systems The “Simple” Case of Distributed Database Systems?
Client/Server Environments 研究生课《高级数据库系统技术》 data(object)server n smart clients(workstations) objects stored and administered on server objects processed (accessed and modified ) on workstations [sometimes on the server too] CPU-time intensive applications on workstations GUls, design tools Use client system local storage capabilities com bination with distributed dbs services > distributed server architecture 25 重庆邮电大学空间信息系统研究所
研究生课《高级数据库系统技术》 重庆邮电大学·空间信息系统研究所 25 Client/Server Environments