1. Distributed Database Management System
Lecture 10

2. Major DDBS Architectures
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3. 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
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4. 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
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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
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6. Peer-to-Peer Distributed Systems
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7. Virtual University of Pakistan
ES1
ES2
ESn
ES1
GCS
LCS1
LCS2
LCSn
LIS1
LIS2
LISn
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8. 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
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9. 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
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10. 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
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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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12. 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
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13. 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
Local
Schema
• • •
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