Virtual University of Pakistan Distributed database Management Systems Lecture 03

Virtual University of Pakistan Resembling Setups

Virtual University of Pakistan 3  Distributed Files: A collection of files stored on different computers of a network; not a DDBS  DDBS is logically related, common structure among files, and accessed via same interface

Virtual University of Pakistan 4 Resembling Setups  Multiprocessor System: multiple processors that share some form of memory Processor Unit Processor Unit Processor Unit Memory I/O System Shared Everything Tight Coupling

Virtual University of Pakistan 5 Resembling Setups CPU Memory Computer System CPU Memory Computer System CPU Memory Computer System Shared Secondary Memory Shared Everything Loose Coupling

Virtual University of Pakistan 6 Resembling Setups CPU Memory Computer System CPU Memory Computer System CPU Memory Computer System Switch Shared Nothing

Virtual University of Pakistan 7 Resembling Setups  DDBS is also different from a centralized system having C/S system involving network

Virtual University of Pakistan Reasons for DDBS

Virtual University of Pakistan 9  Local units want control over data.  Consolidate data for integrated decisions  Reduce telecommunication costs.  Reduce the risk of telecommunication failures.

Virtual University of Pakistan 10 Distributed DBMS DBMS 1 DBMS n Global User Node 1Node n Global Schema Local User

Virtual University of Pakistan Promises of DDBSs

Virtual University of Pakistan 12 Transparency User ViewSystem View

Virtual University of Pakistan 13  Data Independence  Two types, Logical Data Independence and Physical Data Independence  A transparent system hides the implementation details from its users

Virtual University of Pakistan 14 Network Transparency  User should not only be free from network management activities rather it should be unaware of even existence of the network  Location Transparency and Naming Transparency

Virtual University of Pakistan Thanks