What is the meaning of three-tier architecture is characterized

Three-tier architecture2007-08-14 10:30One of the characteristics of the IT industry is that it often creates new terms, and the concepts of single-tier and two-tier were created after the emergence of three-tier architecture. Single-tier architecture is the structure of small applications since the 80s, typically based on small databases such as Dbase and Foxbase. The two-tier architecture, which can be understood synonymously as the traditional client/server architecture, is the currently dominant architecture, typically for applications based on large databases such as Oracle, Infomix, and so on. Three-tier architecture is the development of the traditional client/server structure, representing the future of enterprise applications, typically with applications under the Web. The meaning of multi-tier and three-tier architecture is the same, only the details are different.

The reason for these references to two-tier and three-tier is that applications address three levels.

One: the interface layer

The interface layer provides the user with a visual interface through which the user enters data and obtains data. The interface layer also provides a level of security to ensure that the user has access to confidential information.

Two: Logical Layer

The logical layer is the bridge between the interface layer and the data layer. It responds to user requests from the interface layer, performs tasks and grabs data from the data layer, and transmits the necessary data to the interface layer.

Three: Data Layer

The data layer defines and maintains the integrity and security of the data, and it responds to requests from the logical layer to access the data. This layer is usually realized by large database servers, such as Oracle, Sybase, MS SQl Server and so on.

Advantages of Three-Tier Architecture

From a development perspective and from an application perspective, three-tier architecture has greater advantages than either a two-tier or a single-tier structure. Three-tier architecture is suitable for group development, where each person can have a different division of labor and work together to multiply efficiency. When developing a two-tier or single-tier application, each developer should have a deeper understanding of the system, which requires a very high level of competency. When developing a three-tier application, you can combine multiple talents, and only a few people need to have a comprehensive understanding of the system, which reduces the difficulty of development to a certain extent.

The three-tier architecture is a thin client model, where the user only needs a smaller hard disk, less memory, and a slower CPU to get good performance. In contrast, single-tier or fat-client machines are too demanding. My machine is a Pentium 133, 32M RAM, 2.5G hard disk, installed after IE4.0, feel the machine slow a lot of hard disk is only more than 300M of free space, has intended to expand the hard disk to 4G. Imagine if in the future is still a single layer or double mount scrape the mainstream, the hardware update costs will be how much, despite the fact that the computer prices are now falling a lot of individual users can afford, but for enterprises, frequent desktop or desktop mounts are too demanding. But for businesses, the frequent elimination of old machines and the replacement of new ones is a big expense

Another advantage of the three-tier architecture is that it can better support distributed computing environments. Logical tier applications can have multiple machines running on them, taking full advantage of the computing power of the network. The potential for distributed computing is huge and far more effective than upgrading CPUs. Americans have used fractional computing to decrypt passwords that were supposedly never broken in a few months.

The biggest advantage of the three-tier architecture is its security. The user side can only access the data layer through the logical layer, which reduces the number of entry points and shields many dangerous system functions.

How to develop three-tier applications

There are many tools that support three-tier application development, VC 5.0, Delphi 3.0, VB 5.0 are good choices, and Delphi is one of the powerful and relatively easy development tools.

Delphi 3 for the 3-tier structure, proposed three kinds of agents (Broker) and a new generation of database engine to adapt to it.

The first is called Remote Data Broker, the essence of the Remote Data Broker structure is that each client no longer needs a BDE, instead of a centralized BDE, to centralize the management of the way to reduce each client in the BDE must be adjusted to the overhead and complexity. The second is called Constraint Broker, which plays the role of ensuring consistency and data integrity of all client data. The third is the Business Object Broker, which is designed to provide a fast and reliable environment for critical business applications. In order to achieve this high level of performance, BusinessObjectBroker automatically divides the application appropriately and replicates the important business rules to the first zone to achieve the speed requirement

Summary.

Along with the development of the enterprise itself and the complexity of the external environment, the needs of the enterprise are becoming more and more complex, and the development of applications is becoming more and more difficult. A three-tier client/server architecture will help solve this problem.