Functions of the Central Controller and User Privileges in DBMS
In a Database Management System (DBMS), the central controller (usually the Database Administrator - DBA) manages user access and privileges to ensure data security and integrity. Here’s a detailed overview:
1. Functions of the Central Controller
- Granting Privileges: Allow users or roles to perform specific operations on database objects.
- Revoking Privileges: Remove or restrict access rights from users when needed.
- User Management: Create, modify, or delete user accounts and assign roles.
- Role and Group Management: Assign privileges to roles or groups for simplified administration.
- Monitoring and Auditing: Track user access and detect unauthorized activities.
2. Types of Privileges
A. System Privileges
Allow users to perform administrative operations on the database.
| Privilege | Description |
|---|---|
| CREATE USER | Create new database users |
| ALTER USER | Modify user properties |
| DROP USER | Delete a database user |
| CREATE TABLE | Create new tables |
| DROP TABLE | Delete tables |
| CREATE SESSION | Connect to the database |
| ALTER SYSTEM | Modify system-level parameters |
| BACKUP DATABASE | Perform database backup |
B. Object Privileges
Allow users to perform operations on specific database objects like tables, views, or procedures.
| Privilege | Description |
|---|---|
| SELECT | Read data from a table or view |
| INSERT | Add new rows to a table |
| UPDATE | Modify existing rows in a table |
| DELETE | Remove rows from a table |
| EXECUTE | Run a stored procedure or function |
| REFERENCES | Use columns in constraints or foreign keys |
3. SQL Commands for Privilege Management
Granting Privileges
GRANT SELECT ON Employees TO Rahim; GRANT SELECT, INSERT, UPDATE ON Employees TO Rahim;
Revoking Privileges
REVOKE UPDATE ON Employees FROM Rahim; REVOKE SELECT, INSERT ON Employees FROM Rahim;
Conclusion
The central controller or DBA ensures proper access control by granting or revoking privileges, managing users and roles, and auditing database operations. Understanding system and object privileges helps maintain security and integrity in database systems.
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