db2 cour mat

INTRODUCTION TO DATABASE MANAGEMENT SYSTEMS

DefinitionData Base is a collection of data stored in a well

organized manner

Advantages of databaseRedundancy can be reducedInconsistency can be avoidedData can be sharedStandards can be enforcedSecurity restrictions can be appliedIntegrity can be maintainedconflicting requirements can be balanced

Characteristics of DBMSData IndependenceSpeedy handling of spontaneous information

requestsNon-RedundancyVersatility in representing relationships

between data itemsSecurity protectionReal-time accessibility

Types of data bases Hierarchical Database Network Database Relational Database

Hierarchical DatabaseThe Data in this database is stored in the form

of Segments. The Segments will have Parent-Child relationship.

One Parent segment can have more than one

Child Segments and one Child Segment can not have more than one Parent Segment,

I.e., One-To-Many approachEx. IMS/DB

Network DatabaseThe data stored in this type of database in the

form of records and linksHere one record can have more dependent

records and the same record can have more superior records also, I.e., Many-To-Many approach

Ex. IDMS

Relational DatabaseThe data in this type of database is stored in

the form of Tables.The relationship between Tables can be

maintained by using Primary key and Foreign Key relationship

Ex. DB2, Oracle, Sybase etc..

RELATIONAL DATABASE MANAGEMENT SYSTEM

DB2DB2 is a relational database developed by

IBM for computers running under MVSDB2 can be connected to CICS, IMS, TSO

(These three environments provide services

like data communication and control of

transactions)

RDBMS TerminologyThe data in Relational data base is stored in

Table/Relation in terms of rows and columnsRows are called TUPLES and columns are

called ATTRIBUTESNo.of attributes is called as ORDERNo.of Tuples is called as CARDINALITY

Primary key It represents a single column or group of columns

and performs the unique identification of rows(records) in table

Alternate key It is a alternate key to search table, need not maintain

uniqueness

Referential Integrity If table-1 includes a foreign key FK matching the

primary key PK of table-2 , then every value of FK in the first table must either be equal to the value of PK in the second table, then Referential integrity is ensured b/w two tables

Relational OperatorsUnion, Union All

Combining two or more tables or part of tables in row fashion

ex. Select empname from emp where deptno=10

UNION

select empname from emp where deptno=20

Union All eliminates duplicates

JoinCombining two or more tables or part of

tables in column fashionThere is no Join operator in DB2, but we can

achieve it through ‘Select’ statementsThere are Internal Join and Outer Join, Internal

Join looks for matching values of both columns of two tables where as Outer Join does not look for matching.

ex. Select empsal.*, emppsnl.* from empsal,

emppsnl where empid.empsal= empid.emppsnl

Normalization:

It is a formal process of developing data structures in a manner that eliminates redundancy and promotes integrity.

This normalization can be achieved generally by using three forms

1) Elimination of repeating groups

2) Elimination of Partial key dependencies

3) Elimination of inter key dependencies

The following ex. For attaining first normal form:

CREATE TABLE Contacts

(contact_id Number(9,0) Not Null,

l_name Varchar(20) Not Null,

f_name varchar(20),

contact_date1 Date,

contact_desc1 varchar(50),

contact_date2 Date,

contact_desc2 varchar(50));

The elimination of repeating groups can be

done as follows




f_name varchar(20));

CREATE TABLE Conversation


contact_date Date,

contact_desc varchar(50));

The following ex. For attaining second normal form:

CREATE TABLE Employee

(emp_no Number(9,0) Not Null,


f_name Varchar(20)

dept_code Number(3,0)

description varchar(50));

The second normal form can be obtained as follows

CREATE TABLE Employee

(emp_no Number(9,0) Not Null,


f_name Varchar(20)

dept_code Number(3,0));CREATE TABLE Department

Dept_code Number(3,0) Not Null,

Description varchar(50) not null);

Ex. For third normal form CREATE TABLE Contacts



f_name varchar(20)

company_name varchar(20)

company_location varchar(50));

The third normal form can be obtained as follows




f_name varchar(20)

company_id varchar(20));CREATE TABLE Company

(company_id Number(3,0) Not Null,

company_name Varchar(20) Not Null,

company_location varchar(50));

OVER VIEW OF DB2

Major Components of DB2• System service component which supports system operation(system start start up and shut down), operator communication, system log etc.• Locking service component which provides necessary controls for managing concurrent access to data• Data base service component which supports the definition, retrieval and update of user and system data

• Distributed data facility component It provides access to distributed data

Runtime Supervisor• It is resident in the main memory when the application program is executing.•When the program requests some database operation to be performed, control first goes to the runtime supervisor, which uses the control information in the application plan to request the appropriate on the part of the Data Manager.

Data Manager• It performs all the normal access method functions- search, retrieval, update, index maintenance, etc., and also manages the Physical Databases. • It invokes other system components as necessary in order to perform detailed functions such as locking, logging, I/O operations, etc.

Data types in BD2String:

char(x)--> max. val.of ‘x’ is 255

varchar(x)--> max. val.of ‘x’ is 4096 bytes

Graphic(x)--> max. val.of ‘x’ is 127 bytes

Vargraphic(x)

char,varchar are single byte characters set and

graphic and vargraphic are duble byte character set.

Numeric:

Small int(two bytes), Integer(four bytes), Decimal(x,y), float(n)

Date and time:

Date --> mmddccyy

Time --> hhmmss

Time stamp --> mmddccyyhhmmssnnnnnn

STRUCTURED QUERY LANGUAGE (SQL)

SQL (Structured query language) It is used to communicate with database.we can

use this language in two ways I.e., one way is DB2 Interactive another way is by embedding the sql code in application program

Sql is divided into three departments, those areDDL (Data definition language)

operations: CREATE, ALTER, DROP DML (Data manipulation language)

operations: INSERT, UPDATE, DELETE,

SELECT

Contd...

DCL (Data control language)

operations: GRANT, REVOKE

Explanation with ExamplesDDL is used for objects like storage group,

database,table, view, index, Alies,synonyms

ex. CREATE TABLE table name

(col1 data type null constraint,

col2 datatype null constraint, ..)

PRIMARY KEY (key field),

FOREIGN KEY (keyfield)

REFERENCES base table

ON RESTRICT/CASCADE/SET NULL

ALTER TAABLE tablename

ADD colx data type

PRIMARY KEY(key field)

FOREIGN KEY (key field)

REFERENCES base-table

ON DELETE RESTRICT/CASCADE/ SET

NULL DROP TABLE table name

DML is used for manipulation of data in a table

ex.a) INSERT into emp(empno,deptno,name)

values(‘102’,’30’,’xyz’)

b)SELECT * from emp where deptno = 10

c)UPDATE emp SET salary= 10000

where dept.no in (10,20)

d) DELETE from emp where d.no=10DCL is used for to give and take back privileges

from users

ex. REVOKE privileges ON object FROM user

privileges are like select, update, delete, insert

Usage of IN, BETWEEN, LIKE, SUBSTR in sql

IN:

SELECT * FROM emp WHERE deptno

IN(‘10’,’20’)

BETWEEN:

SELECT * FROM emp WHERE salary BETWEEN(1000,3000)

SUBSTR:

SELECT SUBSTR(empname,1,4) from emp

WHERE empno=10

LIKE:

For partial search of a columns LIKE is used.

ex.a)Select empid from emp where empname

LIKE ‘-am-’

b)select empid from emp where empmane

LIKE sub%

Usage of mathematical functions in sql MIN,MAX,COUNT,SUM,AVG

ex. Select MAX(salary) FROM emp

Select MIN(salary) FROM emp

Select COUNT(*) FROM emp

Select AVG(salary) FROM emp

Select SUM(salary) FROM emp

Subquery

It is a query having another query inside the

main query is called subquery

Ex.SELECT ename FROM emp WHERE d.no=(SELECT d.no FROM dept WHERE Loc =

‘chennai’)Correlated subquery

It is a subquery executed for each qualified row

in the outer query.

Ex.1 SELECT name, salary FROM emp WHERE

emp.salary > (SELECT AVG(dept.salary) FROM

dept WHERE emp.deptno=dept.deptno)

Note:

The execution of a subquery happens from inner query to outer and in case of correlated subquery, the execution happens in reverse order, I.e., from outer query to inner query

Ex.2 Select name, deptno, salary from emp x

where salary > (select AVG(salary) from emp GROUP BY deptno HAVING deptno=x.deptno)

DB2 APPLICATION DEVELOPMENT

Steps involved in Execution of an application program

Source Code

Precompiler

Modified source code DBRM

Compile Bind

Link Package or Plan

Load Module

DBRM: (Database request module)It contains the Sql stmt’s extracted from host

language program in precompilation step.DBRM is stored in a member of PDS. This DBRM is the input for the Bind process. A token is placed in DBRM& load module in precompiler step

BIND: It involves in creating executable code for the

sql stmt.’s in DBRM with optimised data access path for sql queries

The out put of bind step, is generating PACKAGE (executable code of one DBRM) or PLAN (executable code of more than one DBRM’s)

performs authorization checks Isolation level parameters, lock size

parameters are declared in this step

Some more notes to run DB2 application program

We run a DB2 application program by submitting JCL or through TSO environment

We have to supply parameters like DB2 subsystem name, plan or package name, name of the program, library of load module etc.

generally to run a db2 application program we use IKJEFT001 utility program

SPUFI(sql processing using file input)It reads the sql statements contained as a text in

sequential file, processes those statements and places in output dataset specified in browse mode

QMF(Query management facility) It is an interactive query tool used to produce

formatted query output.we can type sql query after choosing option 6 from QMF main panel and press PF2 to run the query, for formating the report press PF9 before getting the printout.qmf is for single query execution. QMFPROC can be used to executed multiple sql queries.

Host variable It is a storage space provided by the host language

for the variables declared in sql queries. Purpose is to store the query result in the corresponding host variable.

NULL, NOT NULL, NOT NULL WITH

DEFAULTIn a table, all columns of every record always

can’t contain values, in such cases we can use Null, Not Null, Not Null with default instead of supplying values. These options we should define while creation of Table for particular column.

Nullwhen we don’t supply values for a column of

specified record, null will be supplied by the system.

Not NullThis option specifies that the column can’t have

nulls, always values to be supplied for the columns

declared as Not Null. Generally KEY fields(columns) are defined with

NOT NULL option.

Not Null With DefaultThis option specifies that default values will

be supplied by the system when ever the values are not supplied by us for the columns defined as NOT NULL WITH DEFAULT.

The values generally supplied are Spaces, Zeroes, Time stamp for Character data, Numeric data and Date data respectively.

Insertion of a null indicator By moving -1 null indicator variable

ex. EXEC SQL

INSERT INTO emp

VALUES(:ws-empno, :ws-sex,

:ws-age :ws-age-ind)

END-EXEC

Singleton Select and

CURSOR Technique

We can use sql in interactive mode and batch mode

(by embedding sql statements in the application

program)Embedded sql is of two types one is singleton select

and cursor type In Singleton select we can select only one row,

if the result containing more than one row abends the program

Ex. For singleton Select statement EXEC SQL

SELECT empno, name, sex

INTO :ws-emp-rec FROM emp WHERE

empno = :ws-empno

END-EXEC

CURSOR TechniqueIn CURSOR technique, we can process

multiple rows unlike one row in singleton select. Cursor technique can be achieved by four steps , those are

1)Declare cursor

EXEC SQL

DECLARE empcursor CURSOR FOR SELECT empno,sex,age FROM employee

END-EXEC2)Open cursor

EXEC SQL

OPEN empcursor

END-EXEC

3)Fetch cursor

EXEC SQL

FETCH empcursor INTO : ws-emp-no,

ws-sex, ws-age

END-EXEC4) Close cursor

EXEC SQL

CLOSE empcursor

END-EXEC

FOR UPDATE OF, WHERE

CURRENT OF, WHEN EVERFor Updating any record in the table by using

embedded sql we will use ‘FOR UPDATE OF’ and ‘WHERE CURRENT OF’ phrases

To handle the error conditions in an application program, ‘WHEN EVER’ option will be used.

For the above phrases examples are given in next slide.

Contd.…

EXEC SQL

DECLARE empcursor CURSOR FOR SELECT empno, salary FROM emp FOR UPDATE OF salary

END-EXECEXEC SQL

UPDATE emp SET salary=:ws-salary

WHERE CURRENT OF empcursor

END-EXECEXEC SQL

WHENEVER condition action

END-EXEC

Conditions are like SQL WARNING, SQL

ERROR, NOT FOUND and Actions are like CONTINUE, GO TO

SQLCA(sql communication area)It contains fields (SQLCODE, SQLERRD)

which are used for communicating information describing the success or failure of SQL statement.

EXEC SQL

INCLUDE SQLCA

END-EXEC

Model DB2 application program

(with COBOL)working storage section

01 ws-fetch-flag pic 9(1).

88 ws-fetch-over-cn value 0.

88 ws-fetch-not-over-cn value 1.

01 ws-salnewEXEC SQL

DECLARE empcursor CURSOR FOR

SELECT EMPNO,NAME,DEPT,SALARY

FROM employee WHERE dept= :pa-cry-dept

FOR UPDATE OF salary

END-EXEC

EXEC SQL

INCLUDE SQLCA

END-EXEC

procedure Division.MOVE ‘consultancy’ TO pa-cry-dept.

EXEC SQL

OPEN empcursor

END-EXEC.

SET ws-fetch-not-over-cn TO TRUE.

PERFORM Modify-sal-para

THRU Modify-sal-para-exit

UNTIL ws-fetch-over-cn.

EXEC SQL

CLOSE empcursor

END-EXEC.

STOP RUN.

Modify-sal-para.

EXEC SQL

FETCH empcursor

INTO :empno, :name, :dept, :salary

END-EXEC.

EVALUATE SQLCODE

WHEN SQLCODE < 0

PERFORM X-error-para

THRU X-error-para-exit

WHEN SQLCODE < +100

SET ws-fetch-over-cn TO TRUE WHEN OTHER

COMPUTE ws-salnew = salary * 1.25

EXEC SQL

UPDATE employee

SET salary = ws-salnew

WHERE CURRENT OF empcursor

END-EXEC

END-EVALUATE.

Modify-sal-para-exit.

EXIT.

Important SQL CODES If SQLCODE = 0 --> execution successful

> 0 --> execution successful with warning

< 0 --> execution not

successful

100 --> No rows are matching for a specified

condition

-811 --> Result of an embeded sql stmt’s resulted in retrieval of more than one row

-803 --> Duplicate rows inserted

-603 --> Unique index creation failure due to

duplicate row inserted

-913 --> Dead lock

-918 --> Mismatch of time stamp b/w DBRM & Load module

DB2 INTERNALS

Database ObjectsStorage Group

It is set of DASD volumes given a particular name By using CREATE STORAGE GROUP we can create storage group

Data Base

It is collection of table spaces and index spaces.Byusing CREATE DATABASE we create data base.

Table space

Table spaces are used to store the tables. These are three types, Simple table space, Segmented table spaces, Partitioned table spaces

Table

Combination of rows and columns INDEX

Index is an ordered set of pointers to rows of a base

table. Key has to be supplied for creation of an index

To create index, use CREATE INDEX syntax

VIEW

It is window to the table, may be combination of tables or part of a table. Views are not updatable if the view is combination two tables

ex. CREATE VIEW empview (empno, name) AS

(SELECT empno, name FROM emp) WHERE

salary < 3000SYNONYM

It is an alternate name for a table. The purpose is to

hide the information location of the table It can be

accessed only by the user who creates it, mainly used

in local sub systems, it will be dropped when table is dropped

Ex. CREATE SYNONYM synonym name FOR table name

ALIAS

It is similar to synonym, the differences are, it can be accessed by any user, can be used for local as well as remote subsystems and it will not get dropped even when the table is dropped

Locking Mechanism and Isolation LevelsLock Locking is a mechanism to maintain the

integrity of data in database

Types of locks Sharable --> Read only Update --> Read only Exclusive --> No access to others

Lock levels we can get lock at Row level or at page level

or at Table level or at Table space level we can

specify what lock size to use, while creationof

table space or in bind operation or through

application program.

Isolation levels These specifies lock to be held whether until

next fetch or until end of unit of work There

are two types of Isolation Levels. These Isolation Level will be specified at

BIND time.

1) Cursor Stability In this type of isolation level, lock held until

next fetch By using this we can avoid last update

problem2) Repeatable read In this type of isolation level, lock held until

end of unit of work Incorrect summary is eliminated

Dead lock It is a situation in which two or more

transactions are in simultaneous wait state, each wait for one of others to release a lock on object before it can proceed. Transaction manager will take care this problem suggests for roll back of the task

DB2 RESTART AND RECOVERY SCENARIOS

RecoveryThe data in database will be recovered by

using Recover utility, when any problem occurs like system crash, is called Recover of database.

Active LogIt is DASD dataset used to write the DB2 log

record (containing data changes and significant changes as they occur) is called Active Log.

Archive logWhen Active log is full DB2 copies its

contents to DASD or TAPE dataset called Archive log.

Off-LoadingThe process of transferring data from Active

log to Archive log is called Off-Loading.

COMMIT

By issuing this command the database changes

will be updated and establishes a syncpointRoll back

When any unsuccessful end-of-transaction happens, to undo all the changes upto the last syncpoint (boundary b/w two transactions), roll back command is used.

db2 cour mat

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