Data Base Management System, Formulas and forms for Database Management Systems (DBMS). Krishna University
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Data Base Management System, Formulas and forms for Database Management Systems (DBMS). Krishna University

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Slide 1

DBMS

Data processing

• Data Collection

• Recording

• Sorting

• Classifying

• Calculating

• Retrieving

• Summarizing

• Communicating

Data processing modes

Batch processing: Transactions are collected in a group &

processed together. • On-line (interactive) processing:

Transactions are processed as & when they appear. • Real-time processing:

It is a parallel time relationship with on-going activity & the information produced is useful in controlling the current / dynamic activity.

Traditional Method of Data Storage

• In the traditional approach, we used to store information in flat files which are maintained by the file system under the operating system’s control.

• Application programs go through the file system to access these flat files

Ways of storing data in files – customer data

File System Cont.

• Data used to be stored in the form of records in the files.

• Records consist of various fields which are delimited by a space , comma , tab etc.

• There used to be special characters to mark end of records and end of files.

TRADITIONAL FILE PROCESSING

Data are organized, stored, and processed in independent files of data records. In the traditional file processing approach, each business application was designed to use one or more specialized data files containing only specific types of data records

The business computers of 1980 were used in processing of business records and produce information using file oriented approach or file processing environment At that time that system was reliable and faster than the manual system of record keeping and processing In this system the data is organized in the form of different files. Since that system was the collection of files - so we can say it was a file-oriented system. Following terms was commonly used in this approach or the features of File oriented system.

1. Master file The file that is created only once i.e. at the starting of computerization or a file which rarely changes. For example: In a bank master file the account no, name and balance are entered only once and less frequently changes.

2. File activity ratio The number of records processed one run divided by

total number of records. For example: if we changes 100 records from a bank file containing 200 records then file activity ratio is 100/200 0.5. It should be noted that this ratio of master file is less.

3. Transaction file A file that is created repeatedly after regular interval of time. For example: the payroll file of employee is updated at the end of every month.

4. File volatility ratio It is the number of records updated in a

transaction file divided by total number of records. The file volatility ratio of transaction file is very high.

5. Work file A temporary file that helps in sorting and

merging of records from one file to other. 6. File organization

It means the arrangement of records in a particular order. There were three types of file organizations

• Sequential • Direct • Indexed sequential

LIMITATIONS OF FILE ORIENTED APPROACH

1. Duplicate data / Data Redundancy Since all the files are independent of each other. So

some of the fields or files are stored more than once. Hence duplicacy is more in case of file approach. This duplication of data (redundancy) leads to higher storage and access cost. In addition it may lead to data inconsistency

LIMITATIONS OF FILE ORIENTED APPROACH

2. Data Inconsistency

In this system, data is not consistent. If a data item is changed then all the files containing that data item need to be changed and updated properly. If all the files are not updated properly there may be high risk of inconsistency.

For Example, assume the same data is repeated in two or more files. If change is made to data in one file, it is required that the change be made to the data in the other file as well. If this is not done, it will lead to error during access to the data.

Example: Assume Customer’s details such as Cust_Last_Name, Cust_Mid_Name Cust_First_Name, Cust_Email is stored both in the Customer_Details file and the Customer_Fixed_Deposit file. If the Email ID of one Customer, for example, Langer S. Justin changes from [email protected] to [email protected], the Cust_Email has to be updated in both the files; otherwise it will lead to inconsistent data.

LIMITATIONS OF FILE ORIENTED APPROACH

3. Separated and isolated data

To make a decision, a user might need data from two separate files. First, analysts and programmers to determine the specific data required from each file and the relationships between the data evaluated the files. Then applications could be written in a third generation language to process and extract the needed data. Imagine the work involved if data from several files was needed!

LIMITATIONS OF FILE ORIENTED APPROACH

4. Poor data security

All the files are stored in the flat form or text files. These files can be easily located and trapped because file approach, has no data security.

The data as maintained in the flat file(s) is easily accessible and therefore not secure

LIMITATIONS OF FILE ORIENTED APPROACH

5. Poor data integrity

A collection of data has integrity. A file is said to be have data integrity - it means an item is not be stored in duplicate manner. It has been seen that file oriented system have poor data integrity control. Data integrity has been achieved in DBMS.

LIMITATIONS OF FILE ORIENTED APPROACH

6. Program / Data Dependence Users and application programs need to know exactly where or how the data is stored in order to access it. In file processing system the physical formats of the files are entered in the programs. The change in file means change in program and vice versa.

7. Every operation is programmable The processing tasks like searching, editing, deletion etc should have separate programs. It means there were no functions available for these operations. DBMS have ready- made commands for such operations.

LIMITATIONS OF FILE ORIENTED APPROACH

8. Concurrency problem

It means using a same record at same time by more than one user at the same time. This problem was common in file approach but can be controlled in DBMS.

DBMS • Database: A collection of related data. • Data: Known facts that can be recorded and have

an implicit meaning. • Mini-world: Some part of the real world about

which data is stored in a database. For example, student grades and transcripts at a university. • Database Management System (DBMS): A

software package/ system to facilitate the creation and maintenance of a computerized database. • Database System: The DBMS software together

with the data itself. Sometimes, the applications are also included.

Slide 1-19

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

Slide 1-20

Typical DBMS Functionality

Other features:

– Protection or Security measures to prevent unauthorized access

– “Active” processing to take internal actions on data

– Presentation and Visualization of data

Where does the DBMS fit in?

Now, the DBMS acts as a layer of abstraction on top of the File system. • You might have observed that, for interacting with the file system, we were using high level language functions for example, the ‘c’ file handling functions. For interacting with the DBMS we would be using a Query language called SQL

Difference Between File and DBMS Operations

Types of Databases

Slide 1-25

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.

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