A Brief Overview of Three Level Architecture
The three-level architecture is an architectural pattern used to develop databases and their associated applications more reliably and efficiently. It is based on the client/server model and consists of three layers: the presentation layer, the data layer, and the business layer.
The presentation layer can be thought of as the ‘face’ of the application; it is the set of tools that the end-user interacts with to create, view, and modify records. This layer is usually GUI-based, allowing for both usability and aesthetics. The data layer provides access to the stored data necessary for the application’s functioning. This layer is responsible for communication with the database, such as queries, updates, and deletions. Finally, the business layer is the engine that services the requests from the presentation layer. It is responsible for performing and coordinating the tasks necessary to fulfill the user’s requests.
Advantages of Three Level Architecture
By separating the application into three layers, each layer can be modified without breaking the application. Assuming that all presentation, data, and business logic are abstracted, changes to one layer do not have to be re-implemented in the other layers. Three-level architecture makes code re-use easier, and increases application reliability and performance.
When designed and implemented properly, three-level architecture increases application scalability and security. Elements of the application can be duplicated or distributed across multiple nodes, each with its own communication protocol and control, and providing a level of fault tolerance and a failsafe. In addition, restricting access to the data layer and hiding it from the presentation layer adds a layer of security and reduces the possibility of unwanted data manipulation or corruption.
Disadvantages of Three Level Architecture
Creating a three-level architecture requires more knowledge and effort than a standard two-tier architecture. Additionally, the application becomes more complex and harder to debug as it is divided into more layers.
Performance can suffer when relying heavily on data abstraction. Additionally, performance can degrade when complex applications make many requests to the server and data manipulation is significant. Further, abstracting the data layer defeats any advantages gained from the use of stored procedure optimization.
Maintenance of Three Level Architecture
When maintaining a three-level architecture, there are several factors to consider, such as minimizing the complexity of the data layer, ensuring that the data and presentation layers are optimized, and ensuring that the application scales efficient with increasing demand.
Software debugging is an important part of maintenance, as it can pinpoint potential issues and bottlenecks. The application should be regularly monitored to ensure reliability and scalability. Additionally, the data layer should be constantly monitored and updated to ensure accuracy and the integrity of the stored data.
Developing Three Level Architecture
Before a three-level architecture can be implemented, the application’s requirements must be thoroughly analyzed. These requirements will dictate the design of the application and the platform which is most suitable for its hosting.
The developer must then focus on optimizing the application for performance. This may involve reworking the data layer, restructuring the database, and/or implementing caching. Depending on the application, the performance could also be enhanced through the use of parallel query execution, real-time data replication, and other techniques.
Data Architecture
When designing an application based on three-level architecture, the data model must be carefully considered. The data model should be planned and designed to allow the application to scale efficiently, as well as to ensure data security and integrity. Data abstraction should be used when feasible, but the model should also take into account the performance and scalability of the application.
Testing
Testing is an important step of the development process. For an application based on three-level architecture, the developer should test the data layer, the presentation layer, and the business layer separately. Different types of tests such as unit tests, performance tests, stress tests, and integration tests should be performed.
In addition, security tests should be performed to ensure that unauthorized access to the data is prevented. One way to do this is to validate data requests before allowing them to pass through the data layer. Any errors or unexpected behaviors should be logged for further investigation.
Data Migration
When transitioning from a two-tier architecture to three-level architecture, data migration is usually required. During this time, special attention must be paid to the process to ensure that data is not lost, corrupted, or rendered invalid. In addition, preparatory steps should be taken to minimize the impact of the migration on the application. This may involve providing additional resources to the server, installing new applications to temporarily store the data while migrating, or rolling back any changes if something goes wrong.
Deployment
When it comes time to deploy a three-level architecture application, the developer must ensure that the environment is properly configured to support it. This includes installing the necessary software and hardware, configuring the network and the operating system, and providing the appropriate security measures. The developer must also ensure that the application is properly tested before deployment to ensure it is reliable, secure, and performing optimally.
