Distributed Database Management Systems: Lecture 11. The main topics covered in this chapter include: major DDBS architectures; client-server architecture; one server multiple clients; server performs most of the data management; query processing; transaction and storage management; peer-to-peer distributed systems;...
Distributed Database Management System Lecture 10 Major DDBS Architectures Virtual University of Pakistan Client-Server Architecture • Basic idea is to distribute functionality • Gives two level architecture • The term used in different meanings; generally C and S refer to processes, may be running at the same machines Virtual University of Pakistan – As you can see in the figure – Server performs most of the data Management; • Query Processing • Transaction and Storage Management – Client, mainly has • application and user interface • a client module of DBMS • Data and lock management cached their sometimes – OS and Communication s/w running at both Virtual University of Pakistan • Client passes user queries to server without trying to understand or optimize them • One Server Multiple Clients • Multiple Servers – One Server at a time – Multiple Servers (transparently) at a time Virtual University of Pakistan Peer-to-Peer Distributed Systems Virtual University of Pakistan ES1 ES2 ES1 ESn GCS LCS1 LCS2 LCSn LIS1 LIS2 LISn Virtual University of Pakistan • Physical data organization at each site defining Local Internal Schemas • On top of that, Local Conceptual Schema • Then the overall view is depicted by Global conceptual schema that supports the External schemas Virtual University of Pakistan • • • • Transparencies Supported Extension of ANSI/SPARC Model Data Independence supported Local Data Dictionary and global exist • Both support local and global mappings Virtual University of Pakistan Interpreting user commands and formats results Checks if user query can be processed Optimized execution strategy Global queries to local ones Coordinates distribution execution of user requests Virtual University of Pakistan 10 Chooses best access path to any data item Makes sure the consistency of local data even in case of failure Physically accesses the data as per the commands generated by query optimizer. Interacts with the OS Virtual University of Pakistan 11 Major DDBS Architectures-III A Multidatabase System • Provides access from multiple, autonomous heterogeneous, and distributed databases Two Major architectures: • • Global Schema Architecture Federated Schema Architecture Virtual University of Pakistan 12 Global Schema Architecture G External Schema G External Schema Global Schema Schema Integration L External Schema Component Schema • • • Component Schema L External Schema Schema Translation Local Schema Virtual University of Pakistan • • • Local Schema 13 ... Virtual University of Pakistan 11 Major DDBS Architectures-III A Multidatabase System • Provides access from multiple, autonomous heterogeneous, and distributed databases Two Major architectures:... most of the data Management; • Query Processing • Transaction and Storage Management – Client, mainly has • application and user interface • a client module of DBMS • Data and lock management cached... a time – Multiple Servers (transparently) at a time Virtual University of Pakistan Peer-to-Peer Distributed Systems Virtual University of Pakistan ES1 ES2 ES1 ESn GCS LCS1 LCS2 LCSn LIS1 LIS2