Introduction to DB2 for z/OS
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DB2 data structures

Introduction to DB2 for z/OS

Data structures are elements that are required to use DB2®. You can access and use these elements to organize your data. Examples of data structures include tables, table spaces, indexes, index spaces, keys, views, and databases.

The brief descriptions here show how the structures fit into an overall view of DB2. The following figure shows how some DB2 structures contain others. To some extent, the notion of "containment" provides a hierarchy of structures.

Figure 1. A hierarchy of DB2 structures
Begin figure description. Relationship of database (with table spaces and index spaces) to storage groups. End figure description.

The DB2 structures from the most to the least inclusive are:

  • DB2 tables
    Tables are logical structures that DB2 maintains. DB2 supports several different types of tables.
  • DB2 indexes
    An index is an ordered set of pointers to rows of a table. DB2 can use indexes to improve performance and ensure uniqueness. Understanding the structure of DB2 indexes can help you achieve the best performance for your system.
  • DB2 keys
    A key is a column or an ordered collection of columns that is identified in the description of a table, an index, or a referential constraint. Keys are crucial to the table structure in a relational database.
  • DB2 views
    A view is an alternative way of representing data that exists in one or more tables. A view can include all or some of the columns from one or more base tables.
  • DB2 schemas and schema qualifiers
    The objects in a relational database are organized into sets called schemas. A schema is a collection of named objects. The first part of a schema name is the qualifier.
  • DB2 table spaces
    A DB2 table space is a set of volumes on disks that hold the data sets in which tables are actually stored. All tables are kept in table spaces. A table space can have one or more tables.
  • DB2 index spaces
    An index space is a DB2 storage structure that contains a single index.
  • DB2 storage groups
    DB2 storage groups are a set of volumes on disks that hold the data sets in which tables and indexes are stored.
  • DB2 databases
    DB2 databases are a set of DB2 structures that include a collection of tables, their associated indexes, and the table spaces in which they reside. You define a database by using the CREATE DATABASE statement.
Parent topic: DB2 concepts

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