Distributed DBMS Architecture Chapter 4 Principles Of Distributed Database Systems,2/e By Ozsu, Patrick Valduriez

Distributed DBMS Architecture

BZUPAGES.COM Architecture of a systems defines its structure, means, the components of the systems, function performed by each component and the relationship among components Architecture of a systems defines its structure, means, the components of the systems, function performed by each component and the relationship among components

BZUPAGES.COM Three major architectures of DDBMS discussedThree major architectures of DDBMS discussed –Peer to peer –Client/Server –Multdatabase These are idealized architectures, practical installations may waryThese are idealized architectures, practical installations may wary

BZUPAGES.COM DBMS Standardization A conceptual framework whose purpose is to divide standardization work into manageable pieces and to show at a general level how these pieces are related to one another. Approaches

BZUPAGES.COM Component-based Components of the system are defined together with the interrelationships between components. Good for design and implementation of the system. However it is difficult to determine functionality of system by seeing its individual component

BZUPAGES.COM Function-based Classes of users are identified together with the functionality that the system will provide for each class. The objectives of the system are clearly identified. But how do you achieve these objectives?

BZUPAGES.COM Data-based Identify the different types of describing data and specify the functional units that will realize and/or use data according to these views

BZUPAGES.COMPracticallyPractically Every aspect has to be consideredEvery aspect has to be considered These Classification schemes are OrthogonalThese Classification schemes are Orthogonal A committee for the DBMS standardization was established in 1972 by ANSI under SPARC (Standards Planning and Requirement Committee)A committee for the DBMS standardization was established in 1972 by ANSI under SPARC (Standards Planning and Requirement Committee)

BZUPAGES.COM Published its initial report in 1975 and then in 1977Published its initial report in 1975 and then in 1977 Its full name being “ANSI/X3/SPARC DBMS Framework”Its full name being “ANSI/X3/SPARC DBMS Framework” Mainly based on Data organizationMainly based on Data organization

BZUPAGES.COM Reference Model Internal View Conceptual View External View External View External View Internal Schema Conceptual Schema External Schema Users

BZUPAGES.COM Dimensions for DDBS Architecture Autonomy refers to the distribution of control not of data. It indicates the degree to which individual DBMSs can operate independently. Types could be Design, Communication and Execution Autonomy. Degree of Autonomy varies in different DDBS architectures Autonomy refers to the distribution of control not of data. It indicates the degree to which individual DBMSs can operate independently. Types could be Design, Communication and Execution Autonomy. Degree of Autonomy varies in different DDBS architectures

BZUPAGES.COM Distribution deals with data. Logically, data appears to be placed at a single place but practically it may be spread at physically different locations Distribution deals with data. Logically, data appears to be placed at a single place but practically it may be spread at physically different locations

BZUPAGES.COM Heterogeneity refers the differences in hardware and software among the individual databases. Like different machines, OS, Data Models, DBMSs, or query languages Heterogeneity refers the differences in hardware and software among the individual databases. Like different machines, OS, Data Models, DBMSs, or query languages

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Major DDBS Architectures-I 1.Client-Server Architecture –The term used in different meanings; generally C and S refer to processes, may be running at the same machines –In the context of DDBS both client and server are machines not processes (Fig 4.4) –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

BZUPAGES.COM Major DDBS Architectures-I & II –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 (A DDBS) DDBS 2- Peer to Peer Distributed Systems Heterogeneous databases at each site, defining Local Internal SchemasHeterogeneous databases 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 (Fig 4.5)On top of that, Local Conceptual Schema, then the overall view is depicted by Global conceptual schema that supports the External schemas (Fig 4.5)

BZUPAGES.COM 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

BZUPAGES.COM 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

BZUPAGES.COM A Multidatabase System Provides access from multiple, autonomous heterogeneous, and distributed databases. Two Major architectures:Provides access from multiple, autonomous heterogeneous, and distributed databases. Two Major architectures: Global Schema Architecture Federated Schema Architecture Major DDBS Architectures-III

BZUPAGES.COM Multidatabase Systems: Architectures External Schema External Schema Global Schema Component Schema Component Schema Local Schema Local Schema Global Schema Architecture Schema Translation Schema Integration Federated Schema Federated Schema Export Schema Component Schema Component Schema Local Schema Local Schema Export Schema Export Schema External Schema External Schema Federated Database Architecture Export Schema

BZUPAGES.COM Global Directory Issues A directory is a database that contains data about data (meta-data). Called global directory in case of a DDBS. Three issues;A directory is a database that contains data about data (meta-data). Called global directory in case of a DDBS. Three issues; A single large or local for each siteA single large or local for each site Location; whether to keep at a single site or distributed.Location; whether to keep at a single site or distributed. Single copy or replicationSingle copy or replication All three issues are orthogonal to each otherAll three issues are orthogonal to each other That concludes chapter 4, questions?That concludes chapter 4, questions?

BZUPAGES.COM Distributed database environments (adapted from Bell and Grimson, 1992)

BZUPAGES.COM Distributed Database Options Homogeneous - Same DBMS at each node. –Autonomous - Independent DBMSs. –Non-autonomous - Central, coordinating DBMS. Heterogeneous - Different DBMSs at different nodes. –Gateways - Simple paths are created to other databases without the benefits of one logical database.

BZUPAGES.COM Distributed Database Options –Systems - Supports some or all of the functionality of one logical database. Full DBMS Functionality - All dist. Db functions. Partial-Multi-database - Some dist. Db functions. –Federated - Supports local databases for unique data requests. »Loose Integration - Local dbs have their own schemas. »Tight Integration - Local dbs use common schema. –Unfederated - Requires all access to go through a central, coordinating module.

BZUPAGES.COM Homogeneous, Non- Autonomous Database Data is distributed across all the nodes.Data is distributed across all the nodes. Same DBMS at each node.Same DBMS at each node. All data is managed by the distributed DBMS (no exclusively local data.)All data is managed by the distributed DBMS (no exclusively local data.) All access is through one, global schema.All access is through one, global schema. The global schema is the union of all the local schema.The global schema is the union of all the local schema.

BZUPAGES.COM Focus on The Following Heterogeneous Environment Data distributed across all the nodes.Data distributed across all the nodes. Different DBMSs may be used at each node.Different DBMSs may be used at each node. Local access is done using the local DBMS and schema.Local access is done using the local DBMS and schema. Remote access is done using the global schema.Remote access is done using the global schema.