The functional components of a database management system are the following:
- File Manager: Manages the allocation of space in disk memory and the data structures used to represent the information.
- Database Manager: Serves as an interface between data and application programs.
- Query Processor: Translates the statements in query languages to low-level instructions. It also converts the user’s request in a more efficient way.
- DDL compiler: Converts the DDL statements into a set of tables that contain metadata, these are stored in the data dictionary.
- Data Files: The data of an organization are physically stored in it.
- Data Dictionary: Contains information regarding the structure of the database.
- Indices: They allow quick access or registration that contain specific values.
- A) Database
User data. Today, almost all databases represent user data as affinities that are data tables. Not all affinities are equally desirable; some are better structured than others. To create well-structured affinities, a process called normalization is performed.
Metadata Because DBMS products are designed to store and manipulate tables, most of them store metadata in the form of tables, sometimes called system tables.
Indices. They are aimed at improving the operation and accessibility of the database. They are used for sorting and quick access to data. Indices are very valuable but come at a cost. Every time a row is updated in an affinity or table, the indexes must also be updated. This is not bad; it just means that the indexes are not free and should be reserved for cases where they are really needed.
Application metadata. They are used to store the structure and format of forms, reports, user queries, and other application components. Normally, the application metadata is not accessed directly, but is done through tools provided by the DBMS for this purpose.
- B) Database administrator system
Design tools. The design tools subsystem has a number of elements that facilitate the design and creation of the database and its applications. Typically includes resources for creating tables, forms, queries, and reports. DBMS products also provide programming languages and interfaces for them.
Runtime Utilities. The runtime subsystem processes application components that are developed using design tools. Other runtime utilities respond to queries and print reports. Additionally there is a runtime component that processes requests from the application program to read and write data from the database.
Database administrator system engine. It is the intermediary between the design tools and the runtime subsystem utilities, and the data itself.
- C) Database applications
A database application consists of forms, queries, reports, menus, and application programs. Application programs must be written in a language that is part of the DBMS or in a language connected to the database through the DBMS.
Shapes. They are used to enter information into the database. Sometimes the identifiers (IDs) of the objects are not displayed in the application. The reason is that they do not exist in the user’s model and therefore have no meaning for him. They are used for the DBMS to identify each row in each table and are called surrogate keys.
Queries. They are used when users want to consult the data to answer questions or to identify particular problems or situations. To express the queries you can use the SQL data access language, another possibility is to use the query for example (Query by example or QBE).
In most DBMS queries can be saved as part of the application, so that they can be rerun. Furthermore, in the queries you can specify parameters, which means that they are structured in such a way that they accept criteria values during their operation.
Reports A report is a presentation that has a format of information from a database. They are usually divided into sections such as Header, titles, groups, details, subtotals, totals and footer. The presentation of information almost always has one or more orderings.
Menus. They are used to organize the various components of the application so that the end user can easily access them, showing them the available options and helping them select the actions they want to perform.
Application programs. The application programs come to be like the glue that allows us to join the rest of the components in a coherent way and allows to carry out processes and calculations to the application. Additionally, there are usually some limitations that DBMS cannot directly enforce in the data structure and that must be encoded in the application program.
