1. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.1 Outline  Introduction à What is a distributed DBMS à Problems à Current state-of-affairs Background Distributed DBMS Architecture Distributed Database Design (Briefly) Distributed Query Processing (Briefly) Distributed Transaction Management (Extensive) Building Distributed Database Systems (RAID) Mobile Database Systems Privacy, Trust, and Authentication Peer to Peer Systems

2. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.2 File Systems program 1 data description 1 program 2 data description 2 program 3 data description 3 File 1 File 2 File 3

3. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.3 Database Management database DBMS Application program 1 (with data semantics) Application program 2 (with data semantics) Application program 3 (with data semantics) description manipulation control

4. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.4 Integrate Databases and Commuinication Database Technology Computer Networks integrationdistribution integration Distributed Database Systems

5. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.5 Distributed Computing A number of autonomous processing elements (not necessarily homogeneous) that are interconnected by a computer network and that cooperate in performing their assigned tasks.

6. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.6 Synonymous terms à distributed data processing à multiprocessors/multicomputers à satellite processing à backend processing à dedicated/special purpose computers à timeshared systems à functionally modular systems à Peer to Peer Systems Distributed Computing

7. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.7 Processing logic Functions Data Control What is distributed …

8. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.8 What is a Distributed Database System? A distributed database (DDB) is a collection of multiple, logically interrelated databases distributed over a computer network. A distributed database management system (D–DBMS) is the software that manages the DDB and provides an access mechanism that makes this distribution transparent to the users. Distributed database system (DDBS) = DB + Communication

9. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.9 A timesharing computer system A loosely or tightly coupled multiprocessor system A database system which resides at one of the nodes of a network of computers - this is a centralized database on a network node What is not a DDBS?

10. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.10 Centralized DBMS on a Network Site 5 Site 1 Site 2 Site 3 Site 4 Communication Network

11. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.11 Distributed DBMS Environment Site 5 Site 1 Site 2 Site 3 Site 4 Communication Network

12. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.12 Implicit Assumptions Data stored at a number of sites  each site logically consists of a single processor. Processors at different sites are interconnected by a computer network  no multiprocessors à parallel database systems Distributed database is a database, not a collection of files  data logically related as exhibited in the users’ access patterns à relational data model D-DBMS is a full-fledged DBMS à not remote file system, not a TP system

13. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.13 Shared-Memory Architecture Examples :symmetric multiprocessors (Sequent, Encore) and some mainframes (IBM3090, Bull's DPS8) P1P1 PnPn M D

14. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.14 Shared-Nothing Architecture Examples :Teradata's DBC, Tandem, Intel's Paragon, NCR's 3600 and 3700 P1P1 M1M1 D1D1 PnPn MnMn DnDn

15. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.15 Manufacturing - especially multi-plant manufacturing Military command and control Electronic fund transfers and electronic trading Corporate MIS Airline restrictions Hotel chains Any organization which has a decentralized organization structure Applications

16. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.16 Transparent management of distributed, fragmented, and replicated data Improved reliability/availability through distributed transactions Improved performance Easier and more economical system expansion Distributed DBMS Promises

17. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.17 Transparency Transparency is the separation of the higher level semantics of a system from the lower level implementation issues. Fundamental issue is to provide data independence in the distributed environment à Network (distribution) transparency à Replication transparency à Fragmentation transparency  horizontal fragmentation: selection  vertical fragmentation: projection  hybrid

18. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.18 Example TITLESAL PAY Elect. Eng. 40000 Syst. Anal.34000 Mech. Eng. 27000 Programmer24000 PROJ PNO PNAME BUDGET ENOENAMETITLE E1J. DoeElect. Eng. E2M. SmithSyst. Anal. E3A. LeeMech. Eng. E4J. MillerProgrammer E5B. CaseySyst. Anal. E6L. ChuElect. Eng. E7R. DavisMech. Eng. E8J. JonesSyst. Anal. EMP ENOPNORESP E1P1Manager12 DUR E2P1Analyst24 E2P2Analyst 6 E3P3Consultant10 E3P4Engineer48 E4P2Programmer18 E5P2Manager24 E6P4Manager48 E7P3Engineer36 E8P3Manager40 ASG P1 Instrumentation 150000 P3CAD/CAM250000 P2Database Develop.135000 P4Maintenance310000 E7P5Engineer23

19. Distributed DBMS© 2001 M. Tamer Özsu & Patrick Valduriez Page 1.19 Transparent Access SELECTENAME,SAL FROMEMP,ASG,PAY WHEREDUR > 12 ANDEMP.ENO = ASG.ENO ANDPAY.TITLE = EMP.TITLE Paris projects Paris employees Paris assignments Boston employees Montreal projects Paris projects New York projects with budget > 200000 Montreal employees Montreal assignments Boston Communication Network Montreal Paris New York Boston projects Boston employees Boston assignments Boston projects New York employees New York projects New York assignments Tokyo