DB2 fundamentals - Part1

7/29/2019 DB2 fundamentals - Part1

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1Copyright 2004, Cognizant Academy, All Rights Reserved

Database & RDBMS concepts: Data,

Database & database Systems

What is Data? A representation of facts or instruction in a form suitable for

communication - IBM Dictionary

What is a Database?

Is a repositoryfor stored data - C.J.Date

What is a database system?

An integrated and shared repository for stored data or collection of storedoperational data used by application systems of some particular enterprise.

Or

Nothing more than a computer-based record keeping system.

Types of Database System

Hierarchical

Network

Relational


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Can be visualized an upside down tree of

data

a single table acts as the "root"

(Parent)of the database from which othertables "branch(Children) out

Child may only have one parent but a

parent can have multiple children

This child/parent rule assures that data is

systematically accessible

Redundancy would occur because

hierarchical databases handle one-to-

many relationships well but do not handle

many-to-many relationships well

Characteristics of Hierarchical Database

Hierarchical Database




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Characteristics of Network Database

Child tables were allowed to have more than one parent

Network model supports many-to-many relationships

The Network model solves the problem of data redundancy by

representing relationships in terms of sets rather than hierarchy




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Customers

Sold -To

Invoices

C# CName

C Addr

I# C# Date

Amt

The concept of a table in which all data is

stored

The database is represented in terms of

Entities, Relations and Attributes.

Database is a collection of tables , constraints

Characteristics of Relational Database

Relational Database




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Advantages of Database systems over File Management Systemare:

Data redundancy

Multiple views

Shared data

Data independence (logical/physical)

Data dictionary

Search versatility

Cost effective

Security & Control

Recovery restart & Backup

Concurrency




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Database & RDBMS concepts: Relational

Properties & Terminology

Relation is a mathematical term for a table - Hence Relationaldatabase is perceived by the users as a set of tables.

All data values are atomic.

Entries in columns are from the same domain

Sequence of rows (T-B) is insignificant

Each row is unique Sequence of columns (L-R) is insignificant

Relation :A table or File Tuple :Row contains an entry for each attribute Attributes :Columns or the characteristics that define the entity Domain: A range of values (or Pool)

Entity : Some object about which we wish to store information

Null :Represents an unknown value Atomic : Smallest unit of data; the individual data value


7/267Copyright 2004, Cognizant Academy, All Rights Reserved

Database & RDBMS concepts:E-R Model

Entity-Relationship model is alogical representation of data for

a business area

Represented as entities,

relationship between entities and

attributes of both relationshipsand entities

E-R models are outputs of

analysis phase i.e they are

conceptual data models

expressed in the form of an E-R

diagram



Database & RDBMS concepts:

Normalization (1NF 5NF)

Normalization is done to bring the design of database to a standardizedmode

1NF : All entities must have a unique identifier, or key, that can be composed

of one or more attributes. All attributes must be atomic and non repeating.

2NF : Partial functional dependencies removed - all attributes that are not a

part of the key must depend on the entire key for that entity.

3NF : Transitive dependencies removed - attributes that are not a part of the

key must not depend on any non-key attribute.

4NF : Multi valued dependencies removed

5NF : Remaining anomalies removed



Database & RDBMS concepts:

Types of Integrity

Entity Integrity: Rule states that no column that is part of a primary keycan have a null value

Referential Integrity: Rule states that every foreign key in the first tablemust either match a primary key value in the second table or must be

wholly null

Domain Integrity: Integrity of information allowed in column



DB2 Overview : DB2 Internal structure

System Services

CICS

TSO

IMS

Relational Data Systems

Data Manager

Buffer Manager

DB2 Utilities

DB2 Optimizer

BufferPools

ActiveLogs

IRLMVSAM

Media Manager

DB2 Table Data DB2Directory

DB2Catalog

DD

F



DB2 objects and Data types:

STOGROUP

STOrage GROUP It is a collection of direct access

volumes, all of the same device

type

The option is defined as a part of

tablespace definition

When a given space needs to be

extended, storage is acquired

from the appropriate stogroup

STORAGE GROUP

DATA BASE(S)

TABLESPACE(S)

TABLE(S)

VIEW(S)

INDEX



DB2 objects and Data types : Database

DATABASE It is a collection of logically related objects - like Tablespaces, Indexspaces,

Tables etc.

A STOGROUP & BUFFERPOOL (is buffer area used to maintain recently

accessed table and index pages) must be defined for each database.

A database may occupy more than one disk space

In a given database, all the spaces need not have the same stogroup




Tablespaces

TABLESPACES Logical address space on secondary storage to hold one or more tables

A SPACE is basically an extendable collection of pages with each page of

size 4K or 32K bytes.

It is the storage unit for recovery and reorganizing purpose

Three Type of Tablespaces - Simple, Partitioned & Segmented

Simple Tablespace

Can contain more than one stored table

Depending on application, storing more than one Table might enable faster

retrieval for joins using these tables Usually only one table is preferred. This is because a single page can

contain rows from all tables defined in the database.

LOAD with replace option deletes all data




Tablespaces

Segmented Tablespace Can contain multiple tables.The tables are stored in different segments.

A Segment consists of a logically contiguous set of n pages.

Segsize parameter decides the allocation size for the tablespace

No segment is allowed to contain records for more than one table

Sequential access to a particular table is more efficient

Mass Delete is much more efficient than in any other Tablespace

Reorganizing the tablespace will restore every table to its clustered order

Lock Table on table, locks only the table, not the entire tablespace

If a table is dropped, the space for that table can be reclaimed with minimum

reorg




Tablespaces

Partitioned Tablespaces Primarily used for very large tables

Only one table in a partitioned TS; 1 to 64 partitions/TS

Numpart parameter specifies the no. of partitions

It is partitioned in accordance with value ranges for single or a combination of

columns. Hence these column(s) cannot be updated

Individual partitions can be independently recovered and reorganized

Different partitions can be stored on different storage groups for efficient

access.




Tables, Views & Index Tables store the data in the form of

Columns of values attached to a specific datatype with allowable valueconstraints

A row for each record.

A View is a subset of columns that are open for a specific purpose. It can be a join of more than one tables.

Indexes are based on the values of data in one or more columns. An index is anobject that is separate from the data in the table.

Indexes are used to enhance performance.

These are discussed in detail further in the course.

EMPNO FIRSTNME MIDINIT LASTNAME WORKDEPT

10 CHRISTINE I HAAS A00

20 MICHAEL L THOMPSON B01

30 SALLY A KWAN C01

Columns

Rows



Views

Views are a logical derivation of a table from other table/tables. A Viewdoes not exist in its own right.

They provide a certain amount if logical independence

They allow the same data to be seen by different users in different ways

In DB2 a view that is to accept a update must be derived from a single

base table



Alias & Synonym

Alias Mean another name for the table.

Aliases are used basically for accessing remote tables (in distributed

data processing), which add a location prefix to their names.

Using aliases creates a shorter name.

Synonym

Also means another name for the table, but is private to the user who

created it.


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Introduction to SQL : Features

SQL or Structured Query Language is A Powerful language that performs the functions of data manipulation(DML),data definition(DDL) and data control or data authorization(DAL/DCL).

A Non procedural language - the capability to act on a set of data and the

lack of need to know how to retrieve it. An SQL can perform the functions of

more than a procedure.

The De Facto Standard query language for RDBMS

Very flexible

SQL - Features

Unlike COBOL or 4GLs, SQL is coded without data-navigational instructions.

The optimal access paths are determined by the DBMS. This isadvantageous because the database knows better how it has stored data

than the user.

What you want and not how to get it

Set level processing & multiple row processing


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Introduction to SQL: Tools

Query Management Facility (QMF) It is an MVS- and VM- based query tool

It allows end users to enter SQL queries to produce a variety of reports and

graphs as a result of this query

QMF queries can be formulated in several ways : by direct SQL stmts, by

means of relational prompted query interface or by query-by-example (QBE).

QBE is similar to SQL in some ways but more user friendly

SPUFI

It supports the online execution of SQL statements from a TSO terminal

Used for developers to check SQL statements or view table details Spufi menu contains the input file in which the SQL statements are coded,

option for default settings and editing and the output file.

Enter option 8.1 on the Cognizant m/f main menu. Provide the input/output

datasets.


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Introduction to SQL : DDL

Data Definition Language

Create Table Syntax:

CREATE TABLE (

Col Name Datatype,)

PRIMARY KEY(Columns)

FOREIGN KEY (Column)

REFERENCESdbname.tablename ON DELETE(SET NULL/CASCADE)

UNIQUE (Col name) (referential

constraint)1. LIKE Table name / View name

2. IN Database Tablespace Name

Foreign Key references dbname.tableon relation condition for delete.

CREATE

ALTER

DROP

DDL

INSERT

SELECT

UPDATEDELETE

DML

GRANT

REVOKE

DCL

SQL


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Introduction to SQL : DDL

Table1 references table2(target) - Table2s Primary key is the foreignkey defined in Table1

The Conditions are CASCADE, RESTRICT & SET NULL (referentialconstraint for the foreign key definition)

Inserting (or updating ) rows in the target is allowed only if there are norows in the referencing table

Alter Table Format:

ALTER : ALTER TABLE

ADD Column Data-type [ not null with default]

Alter allows primary & Foreign key specifications to be changed

It does not support changes to width or data type of a column or droppinga column

Drop Table Format:

DROP : DROP TABLE

Similar statements are there for other database objects


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Introduction to SQL : DDL Rules

Some general rules for RI & Table Parameters Avoid nulls in columns participating in Arithmetic logic or comparisons

Primary key cols cannot be nulls

Limit referential structures to no more than three levels in a direction

Use DB2s inherent features rather than program coded RIs. Do not use RIs on tables built from another RI system

Consider using Fieldprocs or Editprocs or Validprocs


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Introduction to SQL : DCL

GRANT & REVOKE

GRANT : grants the table privileges, plan & package privileges, collectionprivileges, database privileges, use privileges and system privileges

user with a SYSADM privilege will be responsible for overall control of thesystem

The table privileges allowed are SELECT, UPDATE, DELETE, INSERT,(both base tables & views), ALTER(Table) & (Create)INDEX(only to basetables)

There are no specific DROP privilages;the table can be dropped by its owneror a SYSADM

Format of GRANT :

GRANT SELECT, UPDATE(NAME,NO)

ON TABLE EMPLTO A, B, C(or PUBLIC);

GRANT ALL ON EMPL TO PUBLIC;

GRANT EXECUTE ON PLAN PLANA TO USER;

A user having authority to grant privilege to another, also has the authority togrant the privilage with with the GRANT Option


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Introduction to SQL : DCL

REVOKE : this stmt revokes the privileges given to a user. The usergranting the privileges has the authority to REVOKE also.

It is not possible to be column specific when revoking an UPDATE

privilege

REVOKE SELECT ON TABLE EMPL FROM USERA;


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Queries

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