Introduction to DB2

By – Aditi Agrawal

Branch – CS C

En. No. - 120198

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Contents

• Introduction

• Current Editions

• LUW Editions

• System Architecture

• DB2 Interface

• DB2 Objects

• Storage Groups

• Database

• Tablespace

• Table

• Data types

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Content(Cont.)

• Null

• Index

• Referential Integrity

• Referential Integrity - Keys

• References

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Introduction

What is DB2?

• Developed by IBM.

• An abbreviation for ‘IBM Database 2’.

• Introduced in June 1983.

• Support the relational model.

• Platform-specific DB2 product.

• Supports SQL.

• Latest version of DB2 is DB2 10.5.

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Current Editions

There are 4 products in DB2 family –

• DB2 for Linux, UNIX and Windows (informally known as DB2 LUW).

• DB2 for z/OS (mainframe).

• DB2 for i (formerly OS/400).

• DB2 for VM / VSE.

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LUW Editions

IBM has changed the packaging structure in the latest release of DB2

for Linux, Unix and Windows and now offers seven editions –

• Advanced Enterprise Server Edition.

• Advanced Workgroup Server Edition.

• Enterprise Server Edition.

• Workgroup Server Edition.

• Express Edition.

• Developer Edition.

• Express-C.

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System Architecture

Major Components of DB2 –

• SSAS (System Services Address Space)

Thread creation, Program tracing, Logging

• DBAS (Database Services Address Space)

Execution of SQLs, Database objects management, buffer

management, Data read/write, etc.

• IRLM (IMS Resource Lock Manager)

Locking

• DDF (Distributed data facility component )

Distributed Database functionality

• SPAS (Stored Procedure Address Space)

For the execution of the stored procedures

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DB2 Interface

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DB2 Objects

• DB2 manages data through a system of logical and physical

entities called objects.

• Objects that describe the data in the way, users and developers

think about it, are called logical objects.

For example - tables, and views.

• Objects that refer to the way, data is actually stored in the system,

are called physical objects.

For example - database and table space.

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DB2 Objects

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DB2 Objects Hierarchy

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Storage Groups

• A storage group is a named set of storage paths where data can be

stored. Storage groups are configured to represent different classes

of storage available to your database system.

CREATE STOGROUP SG

VOLUMES (V1,V2,V3);

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Storage Groups - (Cont.)

• The number volumes in a storage group can be changed dynamically

as shown below.

ALTER STOGROUP STOUDB6

ADD VOLUMES (V4,V5)

REMOVE VOLUMES (V1,V3);

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Database

• DB2 database is a set of DB2 structures that include a collection of

tables, their associated indexes, and the table spaces in which they

reside.

• One DB2 system can manage up to 65,279 databases.

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Creating a Database

• To create a database use

• To remove a database use

DROP DATABASE DB;

• To change the definition use

CREATE DATABASE DB

STOGROUP SG

BUFFERPOOL (BP0, BP32);

ALTER DATABASE DB

ROSHARE {OWNER, NONE}

STOGROUP SG;

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Tablespace

• A tablespace is a storage location where the actual data underlying

database objects can be kept.

• Three types of Tablespace

– Segmented TS (default)

– Simple TS

– Partitioned TS (for large databases)

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Creating a TS

• Created under an existing DB using

CREATE TABLESPACE TS

IN DB

PRIQTY 10000

SECQTY 1000

PCTFREE 10

FREEPAGE 63

LOCKSIZE ANY

BUFFERPOOL BP0

SEGSIZE 64

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More on TS

• To remove a tablespace use

DROP TABLESPACE TS;

• To change the definition use

ALTER TABLESPACE DB.TS

PRIQTY 200

SECQTY 200

ERASE YES

LOCKSIZE ANY

BUFFERPOOL BP1;

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Table

• The collection of data stored in the form of columns and rows is

known as a table.

• Create table using

CREATE TABLE EMPLOYEE

(EMP_NO SMALLINT NOT NULL,

EMP_NAME CHAR(15),

EMP_ADDRESS VARCHAR(25) NOT NULL,

PRIMARY KEY (EMP_NO));

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More on Table

• To remove a table

DROP TABLE EMPLOYEE;

• To change the definition

ALTER TABLE EMPLOYEE

For example, to add a new field

ALTER TABLE EMPLOYEE

ADD EMP_SALARY INTEGER;

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Data types

• Integer

– 4 bytes (5 if nullable)

• Small int

– 2 bytes (3 if nullable)

• Char(n)

– max. 254 bytes

• Varchar(n)

– max. 4046 bytes

• Time

– 3 bytes (4 if nullable)

• Date

– 4 bytes (5 if nullable)

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Data types - (Cont.)

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Null

• DB2 adds an extra byte to all nullable columns

• This extra byte has the information whether the field contains NULL

or not

• The NULL values do not participate while taking AVERAGE, SUM,

etc.

• Need to have special care while inserting, updating, or retrieving

nullable fields in the host language program.

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Index

• Is a structure used for faster retrieval of data.

• Can be unique or non-unique.

• In DB2, we need to explicitly create a unique index for the primary

key.

• Is stored in B - Tree format.

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Index

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More on Index

• Indexes are created using

CREATE [UNIQUE] INDEX IDX

ON EMPLOYEE(EMP_NO ASC);

• To remove an index

DROP INDEX IDX;

• To change the definition use

ALTER INDEX IDX;

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Referential Integrity

• Referential integrity is a database concept that ensures that

relationships between tables remain consistent.

• There are 3 types of keys –

Unique Key

Primary Key

Foreign Key

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Referential Integrity - Keys

• Unique Key

A unique key is defined in a column (or set of columns) where

no two values are same.

The columns of a unique key cannot contain null values.

A table can have multiple unique keys.

Unique keys are optional and can be defined in CREATE

TABLE or ALTER TABLE statements.

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Referential Integrity - Keys

• Primary Key

A primary key is a key, which is unique in each table.

A table cannot have more than one primary key, and the

columns of a primary key cannot contain null values.

• Foreign Key

A foreign key is a column (or set of columns) which is a primary

key in another table.

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References

• http://en.wikipedia.org/wiki/IBM_DB2

• http://www-03.ibm.com/software/products/en/db2zos

• http://www-01.ibm.com/software/data/db2/linux-unix-windows/

• http://www.cs.umd.edu/class/spring2002/cmsc434-

0101/MUIseum/applications/db2.html

• http://www.webopedia.com/TERM/D/DB2.html

• http://searchdatacenter.techtarget.com/definition/DB2

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