Relational database structure

The database and the database structure are defined in the installation process. The structure of the database depends on whether the database is Oracle Database, IBM® DB2®, or Microsoft SQL Server.

A database that can be perceived as a set of tables and manipulated in accordance with the relational model of data. Each database includes:
  • a set of system catalog tables that describe the logical and physical structure of the data
  • a configuration file containing the parameter values allocated for the database
  • a recovery log with ongoing transactions and archivable transactions
Table 1. Database hierarchy
Component Description
Data dictionary A repository of information about the application programs, databases, logical data models, and authorizations for an organization.

When you change the data dictionary, the change process includes edit checks that can prevent the data dictionary from being corrupted. The only way to recover a data dictionary is to restore it from a backup.

Container A data storage location, for example, a file, directory, or device that is used to define a database.
Storage partition A logical unit of storage in a database such as a collection of containers. Database storage partitions are called table spaces in DB2 and Oracle, and called file groups in SQL Server.
Business object A tangible entity within an application that users create, access, and manipulates while performing a use case. Business objects within a system are typically stateful, persistent, and long-lived. Business objects contain business data and model the business behavior.
Database object An object that exists in an installation of a database system, such as an instance, a database, a database partition group, a buffer pool, a table, or an index. A database object holds data and has no behavior.
Table A database object that holds a collection of data for a specific topic. Tables consist of rows and columns.
Column The vertical component of a database table. A column has a name and a particular data type for example, character, decimal, or integer.
Row The horizontal component of a table, consisting of a sequence of values, one for each column of the table.
View A logical table that is based on data stored in an underlying set of tables. The data returned by a view is determined by a SELECT statement that is run on the underlying tables.
Index A set of pointers that is logically ordered by the values of a key. Indexes provide quick access to data and can enforce uniqueness of the key values for the rows in the table.
Relationship A link between one or more objects that is created by specifying a join statement.
Join An SQL relational operation in which data can be retrieved from two tables, typically based on a join condition specifying join columns.