Thursday, February 5, 2015

Components of Distributed DBMS

The components of Distributed DBMS architecture / List the components of peer-to-peer distributed database management systems / What are the components and sub-components of Distributed DBMS? / List the major and minor components of distributed dbms architecture

Components of Distributed DBMS Architecture

User processor and Data processor are the two major components of Distributed DBMS architecture. These major components handle different user requests using several sub-components in a Peer-to-Peer Distributed DBMS. Those are;

User Processor

  • User interface handler – interpreting user commands when they are given in, and formatting the result sets when the request is answered.
  • Semantic data controller – uses the Global Conceptual Schema to check the integrity constraints defined on database elements and also to check the authorizations on accessing the requested database.
  • Global query optimizer and decomposer – devises a best execution strategy to execute the given user requests in minimal cost (in terms of time, processor, memory). It is like Query Optimizer in Centralized database systems. Only exception is it has to devise a strategy which is globally optimal.
  • Distributed execution monitor – it is the Transaction manager. The Transaction managers of various sites that are participated in a query execution communicate with each other as part of execution monitoring.

Data Processor

  • Local query optimizer – it optimizes data access by choosing the best access path. For example, Local query optimizer decides which index to be used for optimally executing the given query.
  • Local recovery manager – deals with the consistency of the local database. In case of failure, local recovery manager is responsible for maintaining a consistent database.
  • Run-time support processor – it accesses the database physically according to the strategy suggested by the local query optimizer. The run-time support processor is the interface to the operating system and contains the database buffer (or cache) manager, which is responsible for maintaining the main memory buffers and managing the data accesses.

Figure 1 shown below depicts the major and minor components of Distributed DBMS and their communication links. [Image is taken from the book Principles of Distributed Database Systems, Third Edition, by M. Tamer Özsu and Patrick Valduriez.]

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