04. Distributed DBMS Architecture.ppt - search...
Transcript of 04. Distributed DBMS Architecture.ppt - search...
Distributed Database SystemsAutumn, 2007
Chapter 4
Distributed DBMS Architecture
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Introduction
Architecture defines a system’s structure with◦ Components◦ Functions of components, and◦ Their interactions
Purpose of ‘reference architecture’:◦ A framework for discussion◦ Standardization
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4.1 Transparencies in a distributed DBMS
X transparency means the existence of X is not known to users.Closely related to architecture issues.
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4.1.1 Data independence
Same as in centralized DBMS:◦ Logical data independence
applications are immune to changes in schema
◦ Physical independenceapplications are immune to changes in physical storage, and data distribution
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4.1.2 Network transparencyAlso known as “distribution transparency”
4.1.3 Replication transparency
4.1.4 Fragmentation transparencyData fragmentation – the division of relation into smaller fragments at different sites.
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4.2 DBMS Standardization
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4.2.1 ANSI/APARC ArchitectureA 3-level architecture based on data organization
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View Description
External View • How users view the shared data• Commands used:create view … as …
Conceptual View • Synthesis of external views of an enterprise• Commands used:create db …create table …
Internal View • Physical definition and organization of data• Commands used:index on devicesegment definition and allocation
The ASNI/SPARC Architecture (1997)
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External View
External View
Ex ternal View
ConceptualView
Internal View
Ex ternal Schema
Conceptual Schema
Intern al Schema
Users
4.3 Architecture Models for Distributed DDBMS
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4.3 Architecture Models for Distributed DDBMS
Classification of multiple DBs shared by multiple DBMSsCriteria for classification◦ Distribution
0: centralized, 1: C/S, 2: P2P◦ Autonomy
0: tight integration, 1: semi-autonomous, 2: total isolation
◦ Heterogeneity0: homogeneous, 1: heterogeneous
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Distribution
Autonomy
Heterogeneity
1. (A0,D2,H0)P2P homogeneoustightly integrated
P2P homogeneousfederated
P2P homogeneousmultidatabase
2. P2P heterogeneousfederated
3. (A2,D2,H1)P2P heterogeneousmultidatabase
Note 1: the available most advanced commercial product 2 and 3: active research area
Autonomy: the distribution of control
(0) tightly integrated◦ a single image of the entire DB to and user
and a single DBMS(1) semi-autonomous◦ all DBMSs can operated independently but
have to join a federation to make local data sharable
(2) total isolation◦ each DBMS is stand-alone and enjoy 100%
freedom of autonomy
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Distinction between DDB and MDB
In MDB◦ every local data manager is a complete DBMS
with its own DDL, DML and TM
In DDB◦ there is only one data manager with its
dependent component-data-manager at every local site
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The focus of this course is the PRINCIPLES of DDBs (A0, D2, H0)
4.3.1 Distributed DBMS architecture
An architecture based on data organization
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External SchemaExternal Schema External Schema
Global ConceptualSchema
Local Internal Schema
Local ConceptualSchema
Local ConceptualSchema
Local ConceptualSchema
Local Internal Schema
Local Internal Schema
ES
LCS
LIS
GCS
Detailed functional description of DDBMS
Legend
◦ Administrative Role
◦ Data Dictionary/Directory
◦ Processing Unit
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Enterprise Administrator
Global DB Administrator
ApplicationSystem
Administrator
GCS Processor
ES Processor
Local Data ManagerLocal Data Manager
Local DBA
GCS Processor-1
LD/D Local IS
Processor
Internal DB
Conceptual Transformation
Int. StorageInt. DB
Transformation
……
……
GD/D
……
Components of a Distributed DBMS
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Semantic data controller
• Integrity constraint and authorization
Global Query Processor
• decompose and optimize global query
Global Execution Monitor
• Distributed transaction manager
Runtime Support Processor
• physical access to database
Client/Server Systems
A computing model dividing functions between client and server
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Discussion
Why DDB?Compare DDB with CDB, MDB, C/S DB.Do you understand DDB architecture?
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