How DBMS Manages Concurrent Data Access and Solves Data Access Problems Compared to File Systems

 

How DBMS Manages Concurrent Access of Data and Data Access Difficulties over File System

A Database Management System (DBMS) is designed to overcome major limitations of a traditional file system, especially in handling concurrent access of data and data access difficulties. These problems are critical in multi-user environments where data consistency, correctness, and easy retrieval are required.

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1. Concurrent Access of Data

1.1 Problem in File System

In a file system, multiple users can access and modify the same file simultaneously without proper control. This may cause lost updates, inconsistency, and data corruption.

Scenario (File System)

Consider a bank account stored in a file:

Account No: 101
Balance: 10000

Two users access the file at the same time:

• User A deposits 2000

• User B withdraws 1000

Execution Steps

1. User A reads balance = 10000

2. User B reads balance = 10000

3. User A writes balance = 12000

4. User B writes balance = 9000

❌ Final balance = 9000 (incorrect)
✔ Correct balance should be 11000

Reasons

• No transaction concept

• No locking mechanism

• No rollback or recovery support

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1.2 How DBMS Solves Concurrent Access

A DBMS controls concurrent access using:

• Transactions

• Locks (Shared & Exclusive)

• Concurrency control protocols

• Isolation levels

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DBMS Example with SQL

Table Creation

CREATE TABLE Account (
    account_no INT PRIMARY KEY,
    balance DECIMAL(10,2)
);

INSERT INTO Account VALUES (101, 10000);

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Transaction – User A (Deposit 2000)

BEGIN TRANSACTION;

UPDATE Account
SET balance = balance + 2000
WHERE account_no = 101;

COMMIT;

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Transaction – User B (Withdraw 1000)

BEGIN TRANSACTION;

UPDATE Account
SET balance = balance - 1000
WHERE account_no = 101;

COMMIT;

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How DBMS Ensures Correctness

• DBMS applies an exclusive lock on the account row

• Second transaction waits until the first completes

• Transactions execute in a serializable manner

✔ Final balance = 11000 (correct)
✔ Data consistency is preserved

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2. Data Access Difficulties

2.1 Problem in File System

File systems suffer from several data access issues:

• Data redundancy

• Poor data sharing

• Complex program logic

• No data independence

Scenario (File System)

Student data stored in multiple files:

• student_info.txt

• student_marks.txt

• student_attendance.txt

To retrieve complete information of a student:

• Programmer must read multiple files

• Write complex procedural code

• Any change in file structure requires program modification

❌ Difficult maintenance
❌ Low flexibility

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2.2 How DBMS Solves Data Access Difficulties

DBMS organizes data using tables, schemas, relationships, and SQL, providing:

• Logical & physical data independence

• Simple and flexible data retrieval

• Centralized data control

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DBMS Example with SQL

Table Design

CREATE TABLE Student (
    student_id INT PRIMARY KEY,
    name VARCHAR(50),
    department VARCHAR(30)
);

CREATE TABLE Marks (
    student_id INT,
    cgpa DECIMAL(3,2),
    FOREIGN KEY (student_id) REFERENCES Student(student_id)
);

CREATE TABLE Attendance (
    student_id INT,
    attendance_percent DECIMAL(5,2),
    FOREIGN KEY (student_id) REFERENCES Student(student_id)
);

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Insert Sample Data

INSERT INTO Student VALUES (1, 'Rahim', 'CSE');
INSERT INTO Marks VALUES (1, 3.75);
INSERT INTO Attendance VALUES (1, 92.5);

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Easy Data Retrieval Using SQL

SELECT s.name, s.department, m.cgpa, a.attendance_percent
FROM Student s
JOIN Marks m ON s.student_id = m.student_id
JOIN Attendance a ON s.student_id = a.student_id;

✔ Single query retrieves all data
✔ No complex programming
✔ High data sharing and flexibility

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3. Comparison Summary

Feature	File System	DBMS
Concurrent Access	Not controlled	Controlled via locks & transactions
Data Consistency	Not guaranteed	Guaranteed (ACID)
Data Access	Program dependent	SQL based
Data Redundancy	High	Minimal
Data Independence	Not supported	Supported

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Conclusion

A DBMS effectively manages concurrent access using transactions and locking mechanisms, ensuring data consistency even in multi-user environments. It also resolves data access difficulties by providing structured storage, SQL-based retrieval, and data independence. Compared to file systems, DBMS offers better reliability, scalability, and ease of data management, making it the preferred choice for modern applications.