Distributed Database Management Systems: Lecture 4

Distributed Database Management Systems: Lecture 4. The main topics covered in this chapter include: fragmentation transparency; responsibility of transparency; performance improvement; through data localization; inter-query and intra-query parallelism; database design; query processing; concurrency control;...

Distributed Database  Management System  Lecture 04 Virtual University of Pakistan Fragmentation  Transparency Virtual University of Pakistan Responsibility of Transparency Transparency is desirable but there  is a compromise between level of  Transparency and difficulty/cost The language/Compiler: to provide  uniform method of manipulating  data. Avoid connectivity details.  Operating System: already  provides in form of Device Drivers Virtual University of Pakistan Responsibility of Transparency Can also provide network Trns. However  not all provide complete Third layer is DBMS. Uses features of  Operating System in particular for  network transparency Practically, we get combination of all  three Virtual University of Pakistan Lan T R/F T NwT DI Data Layers of Transparency Virtual University of Pakistan Reliability in DDBS Reliability through Distributed  Transactions: Avoids simple point of failure Concurrency Issues: Transaction involving  multiple records Failure Recovery: Involving multiple sites Virtual University of Pakistan Performance Improvement Through Data Localization – Each site handles a portion of data, so  contention of CPU or I/O is relatively less – Reduces remote access delays; no matter  how fast networks are latency delays are  there and may be unacceptable in certain  case Inter­query and Intra­query  parallelism Virtual University of Pakistan Complicating Factors In case of Replication: –Choose the appropriate copy –Update impact reflected on all  replicas Failure Recovery Virtual University of Pakistan Complication Factors Complexity Cost: hardware and also the  duplication of manpower Distribution of Control may cause  problems if not used cautiously  Virtual University of Pakistan The Problem Areas Virtual University of Pakistan 10 Database Design Query Processing Concurrency Control Virtual University of Pakistan 11 OS Support Heterogeneity  Relationship among  them  Virtual University of Pakistan 12 Directory Management Query Processing Distributed DB Design Reliability Concurrency Control Deadlock Management Virtual University of Pakistan 13 Thanks Virtual University of Pakistan ... ? ?Database? ?Design Query Processing Concurrency Control Virtual University of Pakistan 11 OS Support Heterogeneity  Relationship among  them  Virtual University of Pakistan 12 Directory Management. .. Virtual University of Pakistan 12 Directory Management Query Processing Distributed DB Design Reliability Concurrency Control Deadlock Management Virtual University of Pakistan 13 Thanks Virtual University of Pakistan... Layers of Transparency Virtual University of Pakistan Reliability in DDBS Reliability through? ?Distributed? ? Transactions: Avoids simple point of failure Concurrency Issues: Transaction involving