1. Module 2: Database Environment

2. Overview Three –Level ANSI-SPARC Architecture Database language
Data Models and Conceptual Modeling
Function of DBMS
Components of DBMS
Multi user DBMS Architecture
Data Dictionary

3. Three –Level ANSI-SPARC Architecture
External Level
The users view of database.---Relevant to the particular user
Conceptual Level
The community view of the database. ----what data is stored in database, and relationships
Internal Level
The physical representation of the database on the computer---How data is stored in database.

4. Three –Level ANSI-SPARC Architecture
User1
User2
User n
View1
View2
View n
External Level
Conceptual
Level
Conceptual Schema
Internal Schema
Internal
Level
Physical Data Organization
Database

5. Database Languages A data sublanguage consists of two parts DDL
A Descriptive language that allows the DBA or user to describe and name of entities required for the application and relationships that may exists between the different entities
DML
A language that provides a set of operations that support the basic data manipulation operations on the data held in the database.

6. Database Languages DML Insertion Update (Modification)
Retrieval (Selection)
Deletion

7. Database Languages Types of DML Procedural
A language that allows the user to tell the system exactly how to manipulate the data.
Treats records individually
Non Procedural
A language that allows the user to state what data is needed rather than how it is to be retrieved.
Statements operate sets of records

8. Data Models and Conceptual Modeling
An integrated collection of concepts for describing data, relationships between data and constraints on the data in an organization.
Object Based Data Models
Record Base Data Models
Physical Data Models
Conceptual Data Models

9. Object Based Data Models
This model use the concepts such as entities, attributes and relationships.
Entities (Person, Place or thing, concept or event)
Attributes (Properties)
Relationships (association between entities)

10. Record Base Data Models
Database consists of number of fixed-format records of possibly different types , each record define number of different fields and each typically fixed length.
Relation Data Model
Network Data Model
Hierarchical Data Model

11. Relation Data Model
The relational data model is the based on the concept of mathematical relation
DeptId
Depart Name 1
Accounts 2
H.R 3
MIS
Empid
Name
Age
Deptid 1
Ali 34 2
Ahmad 30 3
Bilal 40 4
Waseem

12. Network data Model
In the network model, data is represented as collection of records and relationships are represented by sets.

13. Hierarchical data modal
The hierarchal modal is a restricted type of network model .again data is represented as collection of records and relationship are represented by sets

14. Physical data model
Physical data model is describe how save data in computer, representing information such as record structures ,record ordering and access path .

15. Conceptual modeling
We can see that the conceptual schema is the heart of the database. It supports all the external views and is, in turn, supported by the schema.

16. Functions of DBMS Data storage, retrieval and update
A DBMS must furnish users with the ability to store, retrieve and update data in the database.
A user accessible catalog
A DBMS must furnish a catalog in which descriptions of data items are stored and which is accessible to users

17. Functions of DBMS Transaction Support
A DBMS must furnish a mechanism which will ensure that either all the Updates corresponding to a give transaction are made or that none of them are made
Concurrency control services
A DBMS is must furnish a mechanism to that the database is updated correctly when multiple users are updating the database concurrently.

18. Functions of DBMS Recovery services
A DBMS must furnish a mechanism for recovering the database in the event that the database is damaged in any way.
Authorization services
A DBMS must furnish a mechanism to ensure that only authorized users can access the database
Support for Data Communication
A DBMS must be capable of integrating with communication software.

19. Functions of DBMS Integrity Services
A DBMS must furnish a means to the both the data in the database and changes in the data flow certain rules.
Services to data independence
A DBMS must include facilities to support independence of programs from the structure of the database.
Utility Services
A DBMS should provide a set of utility services

20. Multiple –user DBMS architectures
Teleprocessing
File-server
Clint-server

21. Data Dictionaries
Data Dictionary: a repository of information description the database that is the metadate or the data about the data
The names of users authoresses to use DBMS;
The names of the data items in the database ;
The data items that each use can access and the type of allowed for example, insert, update, or read access.