Database Developers Resources

Who is a Database developer?

Database developers are a group of people or individual persons who are responsible for the development of a database. Once the development phase is over, the database developers also take over the maintenance of the system, which is known as database maintaining. The responsibilities of database developers are:

Physical organisation and schema modification
Definition of schema
Access methods and storage structure definition

What is the basic approach followed in database development?

The task of the database developing includes the following two parallel activities. The first activity involves the structure of the database and the design of the data content; the second is related to the overall database application. The two activities influence each other strongly. Database design methodologies focus similarly to software design and there are six phases, which are logical database design, physical design database, database implementation and tuning, requirements and analysis, choice of DBMS and conceptual database design.

What are logical and physical database designs?

Logical Database design – the aim of this design is to create external schemas and conceptual schemas in the data model of the DBMS selected type by mapping the schemas that were produced in the conceptual design phase. The mapping stage can be performed in two phases:

System independent mapping – does not consider any characteristics or specific cases from the data model, because it is based totally on the business rules and the user requirements.
Designing schema for specific DBMS – the logical design is developed for specific organisations or users. The specific database owners define the database limitations, constraints, available resources and the economic feasibility.

Physical database design – the process of choosing the specific access paths and storage structures for each database file so that they give out a good performance for each database application. Each DBMS will offer a variety of options for the access paths and file organisation. Once the specific DBMS has been chosen, then the physical databases choice is restricted and the most appropriate structure for the database file must be chosen. There are certain criteria which may be used to guide the choice of options for physical database designs:

Throughput – the number of transactions that are processed per unit time. It must be measured under the peak conditions of the system.
Space utilisation – how much space is required in the memory to be able to store the database files. The structure of their access paths must also be low.
Response time – this must remain low. Between the submission of the database transaction that needs execution and the response, this is known as the response time.

What is database tuning?

After the logical and physical design phase, the database designer then has to implement the database in a smooth and successful way. It the database then has to be converted from an earlier computerised system, to a new one, the appropriate conversion routes may be needed that format the data that leads into the new database. This may include the following objectives:

To minimise the response time of transactions and queries
To improve the overall throughputs of the transactions
To make the execution of the application faster

What constitutes the requirements and analysis phase of database development?

The purpose of the analysis and requirements phase is to find out the requirements of the client, the business rules and the nature and size of the organisation. This information collection from various systems and people is called requirements collection and analysis. The main activities from this phase are:

To analyse the transaction frequencies and their types and analyse the flow of information within the system
Identify the database users
Collect and ask for the requirements from the specific users of the database
Analyse the existing documents, such as forms, reports, organisation charts and policy manuals

Why should the correct type of DBMS be used in database development?

There are such a lot of factors to consider in database design that is dependent on the choice of DBMS used. Some of them are economical and some are technical.

The economical factors take into consideration the financial status of the support organisations vendor. The factors that can be considered when estimating costs are maintenance costs, personal costs, software acquisition costs, hardware acquisition costs, operating costs and training costs.
The technical factors take into consideration the types of DBMS, the development tools availability, the types of high level languages and the access paths and storage structures that support the DBMS etc.

What is conceptual design database?

The goal of this is to produce a conceptual schema that is independent of the specific DBMS type. There are two activities to this phase:

Transaction and application design – once a database system has been designed, the database developer is only too aware of the known applications that will run effectively on the database. An important part of database design is to know which functional characteristics will work early on in the design process. An important method that can specify the transactions at virtual level are to identify their functional behaviours and their input/output. The three methods of transactions are:

Update transaction – this transaction enables users to enter new data or the modification of existing data within the database
Mixed transaction – this transaction can be used for more complex database applications that perform updates and retrievals
Retrieval transaction – this transaction is used to produce reports or retrieve data that is displayed on a screen

Conceptual schema design – an independent DBMS type model should be used during this phase of the design. The reasons for this are:

They are simple to understand
The DBMS type can be changed and the design can be amended without it affecting the independent DBMS conceptual schema
The model chosen in this phase should have the characteristics of simplicity, expressiveness, formality, diagrammatic representation and minimalism.
The conceptual schema’s diagrammatic representation can act as a good tool of communication between analysts, designers and end users.

Only some of the database transactions may be known at the time of design. After the system has been implemented, new transactions will continuously be identified and implemented.