Database is a systematic collection of data. Databases support storage, creation, access, manipulation and deletion of data. Databases make data management easy.
The architecture of a database system is very much influenced by the primary computer system on which the database system runs. Database architecture can be seen as either single tier or multi-tier. An architecture having n-tier splits the entire system into related but independent n modules that can be independently customized, changed, altered, or replaced. A DBMS architecture is depending on its design and can be of the following types:
2.1.1 Three-Tier Architecture
A 3-tier architecture separates its tiers from each other based on the complexity of the users and how they use the data present in the database. It is the most widely used architecture to design a DBMS. A 3-tier application is an application program that is structured into three major parts; each of them is distributed to a different place or places in a network. These 3 divisions are as follows:
• Database (Data) Tier
• Application (Middle) Tier
• User (Presentation) Tier
The intention of a database is to have a collection of data stored together to serve multiple applications as possible. Hence a database is often conceived of as a repository of information needed for running certain functions in a corporation or organization. Such a database would permit not only the retrieval of data but also the continuous modification of data needed for control of operations. It may be possible to search the database to obtain answers to queries or information for planning purpose. The main concepts that exists in the database are listed below:
A database schema is the skeleton structure that represents the logical view of the entire database. It defines how the data is organized and how the relations among them are associated. It formulates all the constraints that are to be applied on the data.
A database schema defines its entities and the relationship among them. It contains a descriptive detail of the database, which can be depicted by means of schema diagrams. It's the database designers who design the schema to help programmers understand the database and make it useful.
A database schema can be divided broadly into two categories âˆ’