Below is a complete, exam-ready explanation of Centralized Architecture and Client–Server Architecture under the broader topic of Parallel Databases / Database System Architectures.
⭐ CENTRALIZED & CLIENT–SERVER ARCHITECTURES
(Under Parallel / Distributed Database System Architectures)
Database architectures describe how database components—CPU, memory, storage, and users—are organized for processing queries.
Although Parallel Databases typically cover shared memory, shared disk, and shared nothing systems, Centralized and Client–Server Architectures form the foundational structures from which parallel architectures evolved.
Let’s discuss both in detail.
⭐ 1. CENTRALIZED DATABASE ARCHITECTURE
In a Centralized Architecture, the entire database system is located on a single machine.
✔ Single processor
✔ Single memory
✔ Single database server
✔ Single storage system
✔ Multiple users may access it, but processing happens in one place
It is also known as a Stand-Alone DBMS.
⭐ Architecture Diagram (Text Form)
+------------------------+
| Central Database |
| (CPU + Memory + Disk) |
+------------------------+
/ | \
/ | \
User1 User2 User3
Users connect through terminals, but all computation happens in the central server.
⭐ Characteristics
- Database resides on one system
- Query processing and transaction execution both occur on central machine
- Users interact via:
- Dumb terminals
- Web interfaces
- Remote login
⭐ Advantages
- Simple to manage
One server → easy maintenance and administration. - Strong consistency
Since only one copy of the database exists. - Secure environment
Central control over authentication & authorization. - No distributed overhead
No network latency or distributed transaction issues.
⭐ Disadvantages
- Single point of failure
If the server crashes → whole system down. - Scalability limitations
Cannot easily expand CPU/memory beyond a limit. - Performance bottleneck
Heavy load slows down the system. - Not suitable for large organizations
Cannot handle distributed workloads.
⭐ Use Cases
- Small businesses
- Academic labs
- Local departmental databases
- Legacy systems
⭐ 2. CLIENT–SERVER ARCHITECTURE
A Client–Server Architecture divides the DBMS functionality between:
- Client (front-end) — user interface, application logic
- Server (back-end) — query processing & database storage
It allows multiple clients to access a single server simultaneously.
This is the foundation of modern relational DBMS systems.
⭐ Architecture Diagram (Text Form)
+-----------+ +---------------------+
Client →| Front End |<------->| Database Server |
| Application| | (SQL Engine, DBMS) |
+-----------+ +---------------------+
Clients issue SQL requests → server executes → returns result.
⭐ Characteristics
- Database stored on server
- Clients run GUI, forms, or applications
- Communication via network protocols (TCP/IP)
- Server performs:
- Query parsing
- Optimization
- Concurrency control
- Transaction management
⭐ Types of Client–Server Architectures
✔ 1. 2-Tier Architecture
- Client → directly interacts with database server
- Thin server / Thick client
- Used in desktop applications
Client (App + SQL) ↔ DB Server
✔ 2. 3-Tier Architecture
- Client (UI) → Middle Tier (Business Logic) → DB Server
- Used in enterprise systems
Client UI → Application Server → Database Server
✔ 3. N-Tier Architecture
- Multiple application tiers
- Cloud-based and large-scale systems
⭐ Advantages
- Improved performance
- Server handles heavy DB operations
- Client handles UI
- Scalability
- Can add more clients
- Distributed load
- Better security
- Authentication on server
- Access control at various tiers
- Parallel Processing
- Multiple clients execute queries concurrently
- Server manages concurrency control
- Better maintainability
- Easy to update server or client separately
⭐ Disadvantages
- Network dependency
- Performance depends on network speed & reliability
- Complex administration
- Requires skilled DBA for tuning, security, backups
- Server overload
- Too many clients → high traffic → bottleneck
- Potential security risks
- Exposed server endpoints require strong protection
⭐ Centralized vs Client–Server Architecture
| Feature | Centralized | Client–Server |
|---|---|---|
| Processing | All on one server | Split between client & server |
| Scalability | Low | High |
| Network dependency | No | Yes |
| Failure impact | Entire system down | Only one server crash affects |
| Performance | Limited | Better with multiple clients |
| Use case | Small systems | Enterprise systems |
⭐ Role of These Architectures in Parallel Databases
Parallel databases expand on these by enabling:
✔ Multiple servers (not just one)
✔ Data partitioning
✔ Parallel query execution
✔ High throughput
✔ Distributed storage
Evolutionary Path:
Centralized DBMS → Client–Server DBMS → Parallel DBMS → Distributed DBMS → Cloud Databases / Big Data Systems
Parallel DBMS architectures extend client–server concepts by adding:
- Multiple processors
- Parallel disk access
- Distributed memory
- Shared-nothing architecture (MPP systems)
Thus, centralized and client–server architectures are the foundation on top of which modern distributed & parallel systems are built.
⭐ Perfect 5–6 Mark Short Summary
Centralized Architecture places the entire DBMS on a single server; all processing happens in one place. It is simple but has low scalability and is a single point of failure.
Client–Server Architecture divides responsibilities: the server manages database operations while clients handle application and UI. It provides better performance, security, and scalability, supporting many users over a network.
Both architectures serve as the foundation of modern parallel and distributed database systems.