dbms

1. Bharati Vidyapeeth (Deemed to be University), Pune
Institute of Management, Kolhapur
DBMS
Dr. Bhaskar V. Patil

2. Data and Information
 DATA: Data is raw, unorganized facts that need to be processed.
 E.g. – Collection of stundent data those are pased 12th examination.
 INFORMATION: It is Process on data. Data presented in a form suitable
for interpretation which provides meaning to data.
 E.g. – Enterence Exam is process on collected data
 DATABASE: A shared collection of interrelated data designed to meet the
varied information needs of an organization.
 DATABASE MANAGEMENT SYSTEM [DBMS]: A collection of
programs to create and maintain a database.
 Define
 Construct
 Manipulate

3. Advantages of Database Processing
 More information from same data
 Shared data
 Balancing conflicts among users
 Controlled redundancy
 Consistency
 Integrity
 Security
 Increased productivity
 Data independence

4. Disadvantages of Database Processing
 Increased size
 Increased complexity
 More expensive personnel
 Increased impact of failure
 Difficulty of recovery
 Cost
 Especially server and mainframe systems

5. Files and Databases
Metadata
“Data about data”
○ Description of fields
○ Display and format instructions
○ Structure of files and tables
○ Security and access rules
○ Triggers and operational rules

6. File Management Systems
 Collection of application programs that perform services for the
end users (e.g. reports).
 Each program defines and manages its own data.
 Provided facilities to extract data and share files, but did not
implement any way to connect records in one file to those in
another.
 Relationships had to be implemented in application code.

7. Limitations of File-Based Approach
 Separation and isolation of data
 Each program maintains its own set of data.
 Users of one program may be unaware of potentially useful
data held by other programs.
 Duplication of data
 Same data is held by different programs.
 Wasted space and potentially different values and/or different
formats for the same item.

8. Database Management System (DBMS)

9. Typical DBMS Functionality
 Define a database: in terms of data types, structures and
constraints
 Construct or Load the Database on a secondary storage medium
 Manipulating the database: querying, generating reports,
insertions, deletions and modifications to its content
 Concurrent Processing and Sharing by a set of users and
programs – yet, keeping all data valid and consistent.
 Other features:
 Protection or Security measures to prevent unauthorized
access
 “Active” processing to take internal actions on data
 Presentation and Visualization of data

10. Main Characteristics of the Database Approach
 Self-describing nature of a database system: A DBMS catalog
stores the description of the database. The description is called
meta-data). This allows the DBMS software to work with different
databases.
 Insulation between programs and data: Called program-data
independence. Allows changing data storage structures and
operations without having to change the DBMS access programs.
 Data Abstraction: A data model is used to hide storage details
and present the users with a conceptual view of the database.

11. Main Characteristics of the Database Approach
 Sharing of data and multiuser transaction processing :
allowing a set of concurrent users to retrieve and to update the
database. Concurrency control within the DBMS guarantees that
each transaction is correctly executed or completely aborted.
OLTP (Online Transaction Processing) is a major part of
database applications.
 Support of multiple views of the data: Each user may see a
different view of the database, which describes only the data of
interest to that user.

12. Advantages of Using the Database Approach
 Controlling redundancy in data storage and in development and
maintenance efforts.
 Sharing of data among multiple users.
 Restricting unauthorized access to data.
 Providing persistent storage for program Objects
 Providing Storage Structures for efficient Query Processing.
 Providing backup and recovery services.
 Providing multiple interfaces to different classes of users.
 Enforcing integrity constraints on the database.
 Drawing Inferences and Actions using rules

13. Disadvantages of DBMSs
 Complexity
 Size
 Cost of DBMS
 Additional hardware costs
 Cost of conversion
 Performance
 Higher impact of a failure

14. Architecture of DBMS
Simple User
Or
End User
Application
Developers
Occasional
Users DBA
Application
Programs
Routine Call Consulted Database
Schema
Object code of
Application
Programs
Precomplier of
DML
Query
Processor
Compiler of
DDL
File Manager Database
Manager
Data File Data
Dictionary
Disk Memory

15. Architecture of DBMS
 Pre-compiler of DML –
 Transforms SQL statements into statements of host language.
 Interact with query processor to generate the appropriate host language code.
 Select, Delete , Update, Insert Statements
 Query Compiler – Transforms queries into a set of low level language which are
forwarded to the database manager component. Statements
 DDL Compiler – Convert set of DDL statements into set of tables
 Database Manager -
 Processed per submitted queries.
 Interface with application programs.
 Data Dictionary-
 It is software module and database containing descriptions and definition concerning the
structure, data elements, interrelationship and other characteristics of organization
DBMS.

16. Architecture of DBMS
Data Manager
The data manager is the central software component of the DBMS. It is
sometimes referred to as the database control system. One of the functions of
the data manager is to convert operations in the user’s queries coming
directly via the query processor or indirectly via an application program from
user’s logical view to a physical file system. The data manager is responsible
for interfacing with the file system. In addition, the tasks of enforcing
constraints to maintain the consistency and integrity of the data, as well as its
security, are also performed by the data manager. Synchronizing the
simultaneous operations performed by concurrent users is under the control
of the data manager. It is also entrusted with the backup and recovery
operations.
 File Manager
Responsibility for the structure of the files and managing the file space
rests with the file manager. It is also responsible for locating the block
containing the required record, requesting this block from the disk manager,
and transmitting the required record to the data manager. The file manager
can be implemented using an interface to the existing file subsystem provided
by the operating system of the host computer or it can include a file subsystem
written especially for DBMS.

17. Architecture of DBMS
Disk Manager
The disk manager is part of the operating system of the host computer
and all physical input and output operations are performed by it . The disk
manager transfers the block or page requested by the file manager so that the
latter need not be concerned with the physical characteristics of the underlying
storage media.
Query Processor
The database user retrieves data by formulating a query in the data
manipulation language provided with the database. The query processor is used
to interpret the online user’s query and convert it into an efficient series of
operations in a form capable of being sent to the data manager for execution.
The query processor uses the data dictionary to find the structure of the relevant
portion of the database and uses the information in modifying the query and
preparing an optimal plan to access the database.

18. Database Users
 Database administrators:
 Responsible for authorizing access to the database, for coordinating
and monitoring its use, acquiring software and hardware resources,
controlling its use and monitoring efficiency of operations.
 Database Designers:
 Responsible to define the content, the structure, the constraints, and
functions or transactions against the database. They must
communicate with the end-users and understand their needs.
 System Analysts
 End Users (Next Slide)

19. End Users
○ Casual: access database occasionally by sophisticated query
language when needed. (Manager)
○ Native: they make up a large section of the end-user population.
Learn only a few facilities that they may use repeatedly. (bank clerk)
○ Sophisticated: These include business analysts, scientists,
engineers, others thoroughly familiar with the system capabilities.
○ Stand-alone: maintain personal database by using well designed
GUI (Turbotax users)