Structure of Database Management System

A Database Management System (DBMS) is software that allows users to define, store, maintain, and manage data in a structured and efficient manner. It acts as an intermediary between data and users, allowing disparate data from different applications to be managed. A DBMS simplifies the complexity of data processing by providing tools to organize data, ensure its integrity, and prevent unauthorized access or loss of data.

In today's data-driven world, DBMS are essential for applications such as banking systems, e-commerce platforms, education, and medical systems. They not only store and manage large amounts of data, but also provide functionality that provides performance, security, and scalability for multiple users with multiple access levels.

It also allows access to data stored in a database and provides an easy and effective method of: 

• We are defining the information.
• Storing the information.
• Manipulating the information.
• We are protecting the information from system crashes or data theft.
• Differentiating access permissions for different users.

Understanding Data Theft in DBMS

Data theft means the illicit extraction or manipulation of sensitive information stored in databases, servers, and other storage systems. This is further defined, in DBMS, as improper access to confidential or sensitive data by unauthorized persons.

This may include information such as personal data, financial records, intellectual property, or trade secrets. As digital data storage has grown, so has the threat of data theft; it is now a primary priority concern with serious impacts on organizations worldwide.

Data theft can be carried out by, among others:

• Hacking and exploiting: Attackers can use DBMS security gaps to access unauthorized sensitive data.
• Insider threats: Employees or contractors compromise privileged access to information.
• Phishing and social engineering: These are techniques that will trick the authorized user into revealing the login credentials to enable intrusion.
• Malware and ransomware attacks: These are malware that make database security vulnerable to attack, thus giving access to attackers to steal data or lock down data until some amount of ransom is paid.

Data theft prevention is not only an issue in sensitive information matters but also for building trust between businesses and clients. Controls over access, periodic audits, real-time monitoring of activities done through the database are effective measures one could consider to reduce the risk. Also, following cyber security protocols and periodic inundation of database systems will reduce most of the vulnerabilities.

Database Architecture vs. Tier Architecture

Structure of  Database Management System is also referred to as  Overall System Structure or Database Architecture but it is different from the Tier architecture of Database. 

• Database Architecture refers to the internal components of the DBMS, including the Query Processor, Storage Manager, and Disk Storage. It also defines the interaction of these components.
  
• Tier Architecture typically refers to the multi-layered setup in an application where DBMS serves as the data layer, but it is distinct from Database Architecture, which refers to the internal structure and levels (internal, conceptual, and external) of the DBMS.

Components of a Database System

Query Processor, Storage Manager, and Disk Storage. These are explained as following below. 

1. Query Processor

It interprets the requests (queries) received from end user via an application program into instructions. It also executes the user request which is received from the DML compiler. Query Processor contains the following components - 

• DML Compiler: It processes the DML statements into low level instruction (machine language), so that they can be executed. 
• DDL Interpreter: It processes the DDL statements into a set of table containing meta data (data about data). 
• Embedded DML Pre-compiler: It processes DML statements embedded in an application program into procedural calls. 
• Query Optimizer: The Query Optimizer executes instructions generated by the DML Compiler and improves query execution efficiency by choosing the best query plan, considering factors such as indexing, join order, and available system resources. For instance, if a query involves joining two large tables, the optimizer will select the best join order to minimize query execution time.

2. Storage Manager

Storage Manager is an interface between the data stored in the database and the queries received. It is also known as Database Control System. It maintains the consistency and integrity of the database by applying the constraints and executing the DCL statements. It is responsible for updating, storing, deleting, and retrieving data in the database. It contains the following components: 

• Authorization Manager: It ensures role-based access control, i.e,. checks whether the particular person is privileged to perform the requested operation or not. 
   
• Integrity Manager: It checks the integrity constraints when the database is modified. 
   
• Transaction Manager: It controls concurrent access by performing the operations in a scheduled way that it receives the transaction. Thus, it ensures that the database remains in the consistent state before and after the execution of a transaction. 
   
• File Manager: It manages the file space and the data structure used to represent information in the database. 
   
• Buffer Manager: It is responsible for cache memory and the transfer of data between the secondary storage and main memory. 
   

3. Disk Storage

It contains the following essential components:

• Data Files: It stores the actual data in the database. 
• Data Dictionary: It contains the information about the structure of database objects such as tables, constraints, and relationships. It is the repository of information that governs the metadata. 
• Indices: Provides faster data retrieval by allowing the DBMS to find records quickly, improving query performance.

Levels of DBMS Architecture

The structure of a Database Management System (DBMS) can be divided into three main components: the Internal Level, the Conceptual Level, and the External Level.

1. Internal Level

This level represents the physical storage of data in the database. It is responsible for storing and retrieving data from the storage devices, such as hard drives or solid-state drives. It deals with low-level implementation details such as data compression, indexing, and storage allocation.

2. Conceptual Level

This level represents the logical view of the database. It deals with the overall organization of data in the database and the relationships between them. It defines the data schema, which includes tables, attributes, and their relationships. The conceptual level is independent of any specific DBMS and can be implemented using different DBMSs.

3. External Level

This level represents the user's view of the database. It deals with how users access the data in the database. It allows users to view data in a way that makes sense to them, without worrying about the underlying implementation details. The external level provides a set of views or interfaces to the database, which are tailored to meet the needs of specific user groups.

Schema Mapping in DBMS

The three levels are connected via schema mapping, ensuring that changes at one level (e.g., the conceptual level) are accurately reflected in the others. This process maintains data independence, allowing changes in physical storage (internal level) without affecting the logical or user views.

Role of Database Administrator (DBA)

In addition to these three levels, a DBMS also includes a Database Administrator (DBA) component, which is responsible for managing the database system. The DBA performs critical tasks such as:

• Database design and architecture.
• Security management: Implementing role-based access control (RBAC), encryption, and ensuring strong authentication measures such as multi-factor authentication (MFA).
• Backup and recovery: Regularly creating backups and preparing recovery plans in case of data loss.
• Performance tuning: Optimizing database performance, including query optimization, indexing, and resource management to ensure the DBMS runs efficiently

Conclusion

Overall, the structure of a DBMS is designed to provide a high level of abstraction to users, while still allowing low-level implementation details to be managed effectively. By separating the physical storage, logical organization, and user views, DBMSs provide a robust framework for managing complex data while ensuring data integrity, security, and performance. This allows users to focus on the logical organization of data in the database, without worrying about the physical storage or implementation details.