Database
Management
Systems
Lecture - 4
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Different Aspect of DBMS - Database Management - Lecture Slides, Slides of Introduction to Database Management Systems
Different aspect of DBMS, Inter Schema Mappings, Logical Data Independence, Physical Data Independence, Data Processing, Transaction Support, DBMS Environments are the main points of this lecture.
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2011/2012
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Database
Management
Systems
Lecture - 4
Today’s Review
Continue 3-L architecture
Data Independence
Different aspect of DBMS
Internal View
DBMS chooses type of data structures
lays out data on storage devices with operating system access methods Docsity.com
Internal View
Internal record : a single stored record
Does not just contain what we see at the conceptual level
DBMS adds other data Docsity.com
Inter-Schema
Mappings
Also a part of 3-level architecture
External/conceptual mapping
Conceptual/Internal
Ext/Con Mapping
Specifies mapping between objects in the external view to those in the logical model
3-Level Architecture
External Level Conceptual Level Internal Level Physical DataOrganization Ext/Con Mapping View 1 View 2 View n ConceptualSchema Internal Schema Database User 1 (^) User 2 User n Con/Int Mapping
Name DoB Deps DepId Rana Aslam 12/09/70 (^5) D Marya Wasti 29/02/80 0 D
First Name: RanaLast Name: Aslam Date of Birth:12 Sep, 1970
Name: R. AslamAge: 24y,10d Dept: Sales Saleem
Saleema
01110011010011100101001010100101010010101…..
BH RH Rana Aslam 120970 5 D001 RH Marya Wasti…
Data Independence
A major outcome of 3-L Arch
The immunity of applications to change in storage structure and access strategy
Changes in lower level do
not affect the upper levels
Don’t take it word to word
Mind the direction please
Data Independence
Logical Data
Independence
Changes in conceptual model do not affect the external views
Immunity of external level from changes at conceptual level
Types of Changes
Adding a new file/index etc. Adding a new field in a file Changing type/size Deleting an attribute
Changes Examples
Changing file organization Index implementation, hash, tree etc. Changing storage medium
3-Level Architecture
External Level Conceptual Level Internal Level Physical DataOrganization Ext/Con Mapping View 1 View n ConceptualSchema Internal Schema Database User 1 (^) User n Con/Int Mapping Conceptual Data Ind PhysicalData Ind