Distributed Database Distributed Database Management System Management System Distributed Database Distributed Database Management System Management System

Lecture 10Lecture 10

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Major DDBS ArchitecturesMajor DDBS ArchitecturesMajor DDBS ArchitecturesMajor DDBS Architectures

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Client-Server ArchitectureClient-Server ArchitectureClient-Server ArchitectureClient-Server Architecture

• Basic idea is to distribute Basic idea is to distribute functionalityfunctionality

• Gives two level architectureGives two level architecture• The term used in different The term used in different

meanings; generally C and S refer meanings; generally C and S refer to processes, may be running at to processes, may be running at the same machinesthe same machines

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–As you can see in the figureAs you can see in the figure–Server performs most of the data Server performs most of the data

Management;Management;• Query Processing

• Transaction and Storage Management

–Client, mainly has Client, mainly has • application and user interface • a client module of DBMS• Data and lock management cached their

sometimes

–OS and Communication s/w OS and Communication s/w running at bothrunning at both

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• Client passes user queries to Client passes user queries to server without trying to server without trying to understand or optimize them understand or optimize them

• One Server Multiple ClientsOne Server Multiple Clients• Multiple ServersMultiple Servers

–One Server at a timeOne Server at a time–Multiple Servers (transparently) at a Multiple Servers (transparently) at a

timetime

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Peer-to-Peer Distributed SystemsPeer-to-Peer Distributed SystemsPeer-to-Peer Distributed SystemsPeer-to-Peer Distributed Systems

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LIS1 LIS2 LISn

LCS1 LCS2 LCSn

ES1 ES2 ESn

GCS

ES1

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• Physical data organization at Physical data organization at each site defining Local Internal each site defining Local Internal SchemasSchemas

• On top of that, Local Conceptual On top of that, Local Conceptual SchemaSchema

• Then the overall view is depicted Then the overall view is depicted by Global conceptual schema that by Global conceptual schema that supports the External schemas supports the External schemas

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• Transparencies Supported Transparencies Supported

• Extension of ANSI/SPARC ModelExtension of ANSI/SPARC Model

• Data Independence supportedData Independence supported

• Local Data Dictionary and global Local Data Dictionary and global existexist

• Both support local and global Both support local and global mappingsmappings

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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

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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

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A Multidatabase SystemA Multidatabase System• Provides access from multiple, Provides access from multiple,

autonomous heterogeneous, and autonomous heterogeneous, and distributed databases. Two Major distributed databases. Two Major architectures:architectures:

• Global Schema Architecture• Federated Schema Architecture

Major DDBS Architectures-IIIMajor DDBS Architectures-IIIMajor DDBS Architectures-IIIMajor DDBS Architectures-III

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Global Schema Architecture

L ExternalSchema

G ExternalSchema

GlobalSchema

ComponentSchema

ComponentSchema• • •

LocalSchema

LocalSchema• • •

Schema Translation

Schema Integration

G ExternalSchema

L ExternalSchema