2 ddb architecture


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2 ddb architecture

  1. 1. 3. Distributed Database Architecture ♦ Distributed Architecture Centralized DBMS on a network Distributed DBMS environment
  2. 2. 3. Distributed Database Architecture ♦ Components of a DDBMS
  3. 3. 3. Distributed Database Architecture ♦ Advantages of a Distributed Database Reduced communication overhead Most data access is local, less expensive and performs better. Improved processing power Instead of one server handling the full database, we now have a collection of machines handling the same database. Removal of reliance on a central site If a server fails, then the only part of the system that is affected is the relevant local site. The rest of the system remains functional and available. Expandability It is easier to accommodate increasing the size of the global (logical) database. Local autonomy The database is brought nearer to its users. This can effect a cultural change as it allows potentially greater control over local data.
  4. 4. 3. Distributed Database Architecture ♦ Disadvantages of a Distributed Database - Complexity - Cost - Security - Integrity control more difficult - Lack of standards - Lack of experience - Database design more complex
  5. 5. 3. Distributed Database Architecture ♦ Shared-memory architecture Examples : symmetric multiprocessors (sequent, Encore) and some mainframes (ibm3090, bull's dps8)
  6. 6. 3. Distributed Database Architecture ♦ Shared-disk architecture Examples : DEC's Vaxcluster, IBM's IMS/VS Data sharing
  7. 7. 3. Distributed Database Architecture ♦ Shared-nothing architecture Examples : Teradata's DBC, tandem, Intel's Paragon, NCR's 3600 and 3700
  8. 8. 3. Distributed Database Architecture ♦ Applications - Manufacturing - especially multi-plant manufacturing - Military command and control - EFT - Corporate MIS - Airlines - Hotel chains Any organization which has a decentralized organization structure.
  9. 9. 3. Distributed Database Architecture ♦ Open database access and interoperability • Open group has formed a working group to provide specifications that will create database infrastructure environment where there is: - Common SQL API that allows client applications to be written that do not need to know vendor of DBMS they are accessing. - Common database protocol that enables DBMS from one vendor to communicate directly with DBMS from another vendor without the need for a gateway. - A common network protocol that allows communications between different DBMSs. • Most ambitious goal is to find a way to enable transaction to span DBMSs from different vendors without use of a gateway.
  10. 10. 3. Distributed Database Architecture ♦ Multidatabase system (MDBS) DDBMS in which each site maintains complete autonomy. - DBMS resides transparently on top of existing database and file systems and presents a single database to its users. - Allows users to access and share data without requiring physical database integration. - Unfederated MDBS (no local users) and federated MDBS.
  11. 11. 3. Distributed Database Architecture ♦ Functions of a DDBMS Expect DDBMS to have at least the functionality of a DBMS. Also to have following functionality: - extended communication services. - extended data dictionary. - distributed query processing. - extended concurrency control. - extended recovery services.