The development of database application system is a software project. Generally, it can be divided into the following stages: 1. Planning 2. Demand analysis. Conceptual model design. Logical design 5. Physical design. Programming and debugging. Operation and maintenance. At present, there is no unified standard for the division of these stages, which are connected with each other and often need retrospective revision. In the development process of database application system, the result of each stage is to write corresponding documents. Each stage is based on the achievements of the previous stage, and the whole development project is well documented, organized, planned and orderly. 1. The main task of planning is to analyze the necessity and feasibility. On the basis of collecting and sorting out relevant data, the relationship between the database application system to be established and the surrounding environment is determined, and the scale, status and function of the application system are comprehensively analyzed and demonstrated. Clarify the basic functions of the application system and divide the scope of database support. Analyze data sources, data collection methods and scope, study data structure characteristics, estimate data scale, and establish basic requirements and business standards for data processing. Plan the allocation of human resources. Put forward requirements for the technical business level of managers and technicians involved in system development and post-maintenance, and evaluate the quality of end users and operators. Draw up the equipment configuration scheme. It is demonstrated in time and space that the processing capacity of computers, networks and other equipment has sufficient internal and external storage capacity, and the response speed, network transmission and input and output capacity of the system should meet the application requirements with margin. Select the appropriate operating system, database management system and other software. The equipment configuration scheme should be comprehensively weighed from the aspects of use requirements, system performance, purchase cost and maintenance cost. Estimate the cost of system development, operation and maintenance. Predict the expected value of system benefits. To make the development progress plan, it is also necessary to make specific arrangements for how to transition the current working mode to the new system. The result of the planning stage is to write a detailed feasibility analysis report and a database application system plan. The contents should include: the positioning of the system and its functions, data resources and data processing capacity, human resources deployment, equipment configuration scheme, development cost estimation, development progress plan, etc. After the feasibility analysis report and the database application system plan are approved, they will become the general outline of the follow-up development work. The development of database application system is a software project. This paper introduces the development steps of database application system. 2. Demand analysis can be roughly divided into three steps. (1) Demand information collection. The collection of demand information is generally based on institutional setup and business activities, and it is carried out step by step from the top to the middle and then to the bottom. (2) Analyze and sort out the demand information. Dfd, dataflowdiagram (DFD) is a formal description of business processes and data relationships in business. Figure 4. 1 is a simple dfd example. Data Dictionary (Dd) describes all the data in the system in detail. The data dictionary contains the following parts. Data item: It is the atomic unit of data. Data group item: consists of several data items. Data stream: Input/output data representing data processing. Data storage: refers to the data to be accessed during processing. The description of data processing process includes: the name, description, input, output, summary of processing work, processing frequency, amount of data processed, response time requirements, etc. Data flow diagram is not only a tool for requirements analysis, but also one of the results of requirements analysis. Data dictionary is the main achievement of data collection and data analysis. (3) Review of demand information. Each stage of the development process should be reviewed to confirm whether the tasks have been completed, and to avoid or correct errors and omissions in the work. Hiring experts outside the project to participate in the review can ensure the quality and objectivity of the review. Review may lead to backtracking or even multiple repetitions of the development process. However, all the expected goals must be achieved before the needs analysis stage can be temporarily ended. The result of the requirement analysis stage is to write a practical and predictable requirement specification with a set of detailed data flow diagrams and data dictionaries. 3. Conceptual model design Conceptual model does not depend on a specific computer system, it is a conceptual structure that purely reflects information needs. Modeling is based on the results of demand analysis, and the data is often abstract. Common data abstraction methods are "aggregation" and "generalization". Er method is a common method in conceptual model design. Using the designed er diagram and the corresponding explanation, the conceptual model design can be completed in three steps. (1) Design the local conceptual model ① Determine the scope of the local conceptual model ② Define the entity ③ Define the connection ④ Determine the attribute ⑤ Draw all the local er diagrams one by one and attach the corresponding documents. The development of database application system is a software project. The development steps of database application system are introduced. (2) The global conceptual model is designed, and the global er diagram is established as follows: ① Determine the type of public entities; ② Merge local er diagrams; ③ Eliminate inconsistent factors; ④ Optimize the drawing of global er diagrams. (3) Review of conceptual model The review of conceptual model is divided into two parts. The first part is user comments. The second part is developer comments. 4. The main goal of logic design logic design stage is to transform the conceptual model into a structured data model supported by dbms on a specific computer. The input elements of logical design include: conceptual model, user requirements, constraints and the characteristics of the selected dbms. The output information of logical design includes: patterns and sub-patterns that dbms can handle, application design guidelines and physical design guidelines. (1) The schema design of relational database of design schema and sub-schema can be completed in four steps. ① Establish the initial relationship model, ② standardize the process, ③ evaluate the model, ④ modify the model, and determine the final model and sub-model after repeated model evaluation and model modification. Write a description of the logical database structure. The development of database application system is a software project. This paper introduces the development steps of database application system. (2) Write the application design guide. According to the design mode and application requirements, plan the architecture of the application program, design the sketch of the application program, specify the outline of the data access function and data processing function of each application program, and provide the logical interface on the program. Write an application design guide. (3) Write a physical design guide. According to the design pattern and application requirements, some important data and documents needed in the physical design stage are sorted out. Such as data capacity of database, data capacity of each relationship (file), application processing frequency, operation sequence, response speed, lra and tv of each application, program access path suggestion and so on. These data and requirements will be directly used in the design of physical database. Write a physical design guide. 5. Physical design Physical design is to configure the physical structure that is most suitable for the application environment for a given logical data model. The input elements of physical design include: mode and sub-mode, physical design guide, hardware characteristics, constraints of os and dbms, operation requirements, etc. The output information of physical design is mainly the structural specification of physical database. Its contents include physical database structure, storage record format, storage record location allocation and access method, etc. The steps of physical design are as follows: (1) Design of storage record structure; Comprehensive analysis of data storage requirements and application requirements; Design of storage record format. (2) Storage space allocation There are two principles for storage space allocation: ① Data with high access frequency should be arranged on fast and random devices as far as possible, and data with low access frequency should be arranged on slower devices. ② Data with strong interdependence should be stored on the same device as far as possible and arranged in adjacent storage spaces as far as possible. In order to improve the system performance, the designed storage records should be taken as a whole, and the physical storage area should be allocated reasonably. Make full use of the characteristics of physical order as much as possible, and assign different types of storage records to different physical groups. (3) Design of access method An access method includes two parts: storage structure and retrieval mechanism. The storage structure defines the access paths that can be used when accessing storage records; The retrieval mechanism defines the access path actually used by each application. The development of database application system is a software project. Introduce the development steps of database application system (4) Performance evaluation of physical design ① The time between query response time and result display is called query response time. Query response time can be further subdivided into service time, waiting time and delay time. In the process of physical design, the performance of the system should be evaluated. Performance evaluation includes time, space, efficiency and overhead. The length of ⊙cpu service time and i/o service time depends on the application design. ⊙cpu queue waiting time and i/o queue waiting time are affected by computer system jobs. Designers can control the communication delay time of distributed database system in a limited range. (2) Storage space The space for storing programs and data. Programs include running applications, dbms subroutines, os subroutines, etc. Data includes user workspace, dbms workspace, os workspace, index buffer, data buffer and so on. Storage space is divided into main storage space and auxiliary storage space. Designers can only control the main memory space within a limited range, such as specifying the allocation of buffers. But designers can effectively control the auxiliary storage space. ③ The following expenses should be considered in the design of expenses and efficiency. With the increase of overhead, the system efficiency will decrease. ⊙ Transaction overhead refers to the time spent from the start of the transaction to the end of the transaction. Updating transactions requires operations such as modifying indexes, rewriting physical blocks, and performing write verification, which will increase additional overhead. Update frequency should be listed as a design consideration. ⊙ Report generation overhead refers to the time from data input to output results. Report generation takes up a long service time of cpu and I/O, so it is necessary to filter out unnecessary report generation in the design. The reorganization of the database is also a big expense. The amount of data and processing frequency should be considered in the design to avoid or minimize the reorganization of the database. In the physical design stage, the process of design, evaluation and modification may be repeated many times, and finally a relatively perfect physical database structure specification is obtained. When building a database, dba can use the tools provided by dbms to configure the database according to the physical database structure specification. When the database is running, dba monitors the performance of the database, and makes timely correction and optimization operations according to the guidelines based on the physical database structure specification to ensure that the database system can maintain efficient operation. 6. After the structure of programming and debugging logical database is determined, the programming of application program design can be carried out in parallel with physical design. Usually, the program module code is debugged in the simulation environment first, and then debugged jointly. The joint debugging work mainly includes the following points: The development of database application system is a software project. This paper introduces the development steps of database application system (1). According to the results of logical design and physical design, the source schema of the database is written with the data language (ddl) provided by dbms, and the target schema is compiled. By executing the target schema, the actual database structure can be established. (2) After the debugging database structure is established, the test data is loaded to make the database enter the debugging stage. Run the application and test (3) loading the actual initial data. Before the database is put into operation, the following work should be done well: (1) Make a feasible scheme to reorganize the database. (2) Formulate failure recovery specifications (3) Formulate system safety specifications (7). After the database is put into operation, the main tasks in the operation and maintenance stage are: (1) to maintain the security and integrity of the database. According to the established safety specifications and fault recovery specifications, when there is a problem with the system security, adjust the authorization and modify the password in time. Find the errors in system operation in time, and modify them quickly to ensure the normal operation of the system. Take the backup and dump of database as daily work. In case of failure, immediately use the latest backup of the database for recovery. (2) Monitor the performance of the system. Using the performance monitoring and analysis tools provided by dbms, the operation of the system can be continuously monitored. When the performance of the database such as storage space or response time decreases, analyze and study immediately to find out the reason and take timely measures to improve it. For example, by modifying some parameters, defragmenting, adjusting the storage structure or reorganizing the database, the database system can maintain efficient and normal operation. (3) On the basis of maintaining the functions and performance of the original system, expand the system functions, adapt to the changes of environment and demand, adopt reasonable opinions of users, expand the original system and add new functions.