DB2 for z/OS and SQL concepts

Many structures and processes are associated with a relational database. The structures are the key components of a DB2® database system, and the processes are the interactions that occur when applications access the database system.

In a relational database, data is perceived to exist in one or more tables. Each table contains a specific number of columns and a number of unordered rows. Each column in a table is related in some way to the other columns. Thinking of the data as a collection of tables gives you an easy way to visualize the data that is stored in a DB2 database.

Tables are at the core of a DB2 database. However, a DB2 database involves more than just a collection of tables; a DB2 database also involves other objects, such as views and indexes, and larger data containers, such as table spaces.

With DB2 for z/OS® and the other DB2 products, you can define and manipulate your data by using structured query language (SQL). SQL is the standard language for accessing data in relational databases.

Submitting SQL statements to DB2
You can use several different methods to send SQL statements to DB2 in several ways.
DB2 Database objects overview
In DB2 for z/OS, you use database objects, such as tables, table spaces, indexes, index spaces, keys, views, and databases to organize and access your data.
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 that provides a logical classification of objects in the database. The first part of a schema name is the qualifier.
DB2 tables
Tables are logical structures that DB2 maintains. DB2 supports several different types of tables.
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.
Aliases
An alias is a substitute for the three-part name of a table or view.
Triggers
A trigger defines a set of actions that are executed when a delete, insert, or update operation occurs on a specified table or view. When such an operation is executed, the trigger is said to be activated.
User-defined types
A user-defined data type is a data type that is defined to the database using a CREATE statement.
Routines
A routine is an executable SQL object. The two types of routines are functions and stored procedures.
Sequences
A sequence is a stored object that simply generates a sequence of numbers in a monotonically ascending (or descending) order. A sequence provides a way to have DB2 automatically generate unique integer primary keys and to coordinate keys across multiple rows and tables.
DB2 system objects
Unlike the DB2 data structures that users create and access, DB2 controls and accesses system objects.
Storage structures
In DB2, a storage structure is a set of one or more VSAM data sets that hold DB2 tables or indexes. A storage structure is also called a page set.
Accessing DB2 data
You can retrieve data by using the SQL statement SELECT to specify a result table that can be derived from one or more tables.
Modifying DB2 data
You can use SQL statements to add, modify, merge, and remove data in existing tables. You can use the INSERT, UPDATE, MERGE, TRUNCATE, and DELETE statements to manipulate DB2 data.
Defining DB2 objects
You can use SQL statements to create, modify, and drop DB2 objects, by using various CREATE, ALTER and DROP statements.
Application processes, concurrency, and recovery
All SQL programs execute as part of an application process. An application process involves the execution of one or more programs, and it is the unit to which DB2 allocates resources and locks.
Packages and application plans
A package contains control structures that DB2 uses when it runs SQL statements. An application plan relates an application process to a local instance of DB2 and specifies processing options.
Character conversion
A string is a sequence of bytes that can represent characters. Within a string, all the characters are represented by a common encoding representation. In some cases, it might be necessary to convert these characters to a different encoding representation. The process of conversion is known as character conversion.
Distributed data
The database managers in a distributed relational database communicate and cooperate with each other in a way that allows a DB2 application program to use SQL to access data at any of the interconnected computer systems.
Distributed data
Distributed data is data that resides on a DBMS other than your local system.
Support for high availability
Because DB2 provides support for high availability, frequently starting or stopping DB2 is not necessary.
DB2 data sharing
With DB2 data sharing, applications that run on more than one DB2 for z/OS subsystem can read from and write to the same set of data concurrently.
pureXML
You can use pureXML® with your client applications to manage XML data in DB2 tables. You can store well-formed XML documents in their hierarchical form and retrieve all or portions of those documents.

Parent topic: What is DB2 for z/OS?

Related concepts:

SQL: The language of DB2