db2 application modified

8/6/2019 Db2 Application Modified

http://slidepdf.com/reader/full/db2-application-modified 1/150



DB2 Objects

There are two types of elements or objects

Data Objects

Accessed under the user’s direction and

by which the user’s data is organized.

System Objects

Controlled and used by DB2



DB2 ObjectsDB2 Objects

Data Objects

Tables

Indexes

Views Tablespaces

Databases

Storage Groups

System Objects

DB2 Catalog

DB2 Directory

Active & Archive Logs Boot Strap Data Set

Buffer Pools

Locks



What is a Database ? ‘Is a repository for stored data’ - C.J.Date

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

suitable for communication’ - IBM Dictionary

What is a database system ?An integrated and shared repository for stored data orcollection of stored operational data used byapplication systems of some particular enterprise.

Or

‘Nothing more than a computer-based record keepingsystem’ .



System Objects

DB2 Catalog

Consists of tables of data about every object defined in the DB2 system.

When an object is created, altered or dropped, a row is inserted, updated

deleted in the Catalog.

DB2 Directory

Contains information required to start DB2 & for its normal operation

Cannot be accessed using SQL

Directory objects are not described in DB2 catalog

Bootstrap Dataset

Contains inventory of all active and archive log datasets.

During installation of DB2, two BSDS datasets are created, kept in different volumes.



Active & Archive Logs

DB2 records all data changes and significant events in active logs as t

occur. In case of failure, it uses this data to recover the lost information.

When the active log is full, DB2 copies the contents of the active log to a DA

or magnetic tape data set called archive logs.

Buffer Pools

Are areas of virtual storage which DB2 uses during execution of an applica

program or an interface SQL, to temporarily store pages of tablespace

There are four different bufferpools named BPO, BP1, BP2, and BP32.



Locks

DB2 guarantees data integrity by using several locking mechanisms. These strategies pe

multiple users from multiple environments to access and modify data concurrently without lo

data integrity.

DB2 supports locking at three levels. Table Space Level, Table Level and Page Level.

DB2 uses locks to control concurrency & prevent inconsistent data.

Data Objects

Tables

All data is stored in tables.

A table is a collection of rows, all having same columns

Rows are records and Columns are fields.

Intersection of a column & row is a Value

SQL is used to access data in DB2 tables.



Indexes

An ordered set of pointers to the data in DB2 table

Stored separately from the table

Each index occupies its own space

Used to Improve performance; Ensure Uniqueness

Multiple indexes can be defined on a table

A table having a primary key will necessarily have a primary unique index.

Views

Is a virtual table derived from one or more base tables

The view definition is stored in a catalog.

Alternate way of representing data that exists in one or more tables

Can include all or some of the columns from one or more base tables

Indexes on Base table can improve the performance operations on the views



TablespacesIs the physical space used to hold one or more tables

Consists of 1 to 64 VSAM LDS can contain upto 64 GB of data

Three types of tablespaces are



Database

A Set of DB2 objects (tables, indexes, tablespaces & views)

One database for one application recommendedDefault Database is DSNDB04

Storage Group (STOGROUP)

A set of Volumes on DASD. Volumes hold the data in which

tables and indexes are actually stored.Up to 133 DASD volumes can be assigned to a single

STOGROUP.

DB2 allocates storage for tablespaces and indexes. When a

tablespace is created, DB2 defines the necessary VSAMdatasets using IDCAMS.



STOGROUP

It is a collection of direct access volumes , all of the same device

type.

The option is defined as a part of table space definition.

When a given space needs to be extended, storage is acquired from

the appropriate STOGROUP.

Max. 133 volumes in a single database.

Syntax:CREATE STOGROUP MAPSG

VOLUMES(SMS001)

VCAT DSNCAT;



DATABASEA collection of logically related objects like

Tablespaces - Indexspaces - Tables etc

Not a physical kind of object – may occupy more than one disk space

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

table & index pages) must be defined for each database.

STOGROUP and user-defined VSAM are the two storage allocation for a DB2 database

definition.

In a given database, all the spaces need not have the Same STOGROUP.

More than one volume can be defined in a STOGROUP. DB2 keep track of which volume was defined first & uses that volume.

Syntax:

Create Database DBMAP STOGROUP MAPSG;



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 & reorganizing

purpose.



simple Tables paces

A simple tablespace can contain one or more tables.A single page of a simple tablespace can containrows from all the tables defined to thetablespace.

In general only one table should be defined persimple tablespace.One table space can be up 64 billion bytesPage size 4kb to 32 kbEach row contains 127 tuples rowsLock is at page levelHere data integrity will be there but data

concurrency will not be there



simple tablespace can contain more than one stored table,though one is usually the best option.

It normally consists of only one VSAM ESDS and maycontain one or more table.

Reading the data of one table requires a sequential read othe Tablespace(tablespace scan) thus increasing I/O anddegrading performance.

Concurrent access to tables in the same tablespace cancause lengthy response delays



LOCKSIZE - indicates the type of locking DB2 performs for the given

TS. (PAGE/TABLE/TABLESPACE)

USING - method of storage allocations –Stogroup or VCAT

PCTFREE - % of space available for future inserts.

FREEPAGE - no. of pages after which an empty page is available.

BUFFERPOOL – BP1,BP2, BP32K

CLOSE – YES/NO- whether the underlying VSAM datasets be closed

each time the table is used.

ERASE – YES/NO - whether physical DASD where the TS reside to bewritten with binary zeros when the TS is dropped.

NUMPARTS - For partitioned tables paces

SEGSIZE - For segmented tables paces



Create simple tablespace

SYNTAXCREATE TABLESPACE SSSVIJTS IN SSSVIJDB USINSTOGROUP

ST0R1PRIQTY 30720SECQTY 10240LOCKSIZE TABLEBUFFERPOOL BP0

CLOSE NO;character: A Cobol word must be formed from followingcharacter



Simple table space

Page1

Table Row 1

Table 1 Row 2

Table 2 Row 1

Page 2

Table 1 Row 3

Table 3 Row 1

Table 2 Row 2

Page 3

Table 1 Row 4

Table 2 Row 3

Table 2 Row 4

Page 4

Table 3 Row 2

Table 3 Row 3



Segmented Tablespaces

The pages within a tablespace are organized into segments and each segment holds

from only one table.

Can hold more than one table. A segmented tablespace is the most efficient type of tablespace for most of the

development efforts.

The space is divided in to equal-sized groups of pages calledsegments, and each segment can contain rows from only one table

Each segment is a group of 4 to 64 pages.Provides improved performance, concurrency and space managem

for multiple tables in a single table space. Related tables can be efficiently placed together in one Table

space.

S t t bl



Segment table space

Segmented table space

Segment 1 Segment 2

Page 1 Page 2 Page 3 Page 4

Table 1 Row 1

Table 1 Row 2

Table 1 Row 3

Table 1 Row 4

Table 1 Row 5

Table 1 Row 6

Table 2 Row 1

Table 2 Row 2

Table 2 Row 3

Table 2 Row 4



Create segment

SYNTAX

CREATE TABLESPACE KSATSIN SSSVJDB USING STOR1

PRIQTY 52

SECQTY 20

ERASE NOSEGSIZE 32

LOCKSIZE PAGE

BUFFERPOOL BP1

close YES;



Partitioned Tablespaces

The tablespace is divided into partitions, and each

partition is stored in one VSAM data set.A partitioned tablespace is divided into componentscalled partitions.

Each partition resides in a separate physical

dataset. DB2 permits 1 to 64 partitions pertablespace.

Only one table can be defined in a partitionedtablespace



Partitioned Tablespaces

SYNTAX

CREATE TABLESPACE SALESHX IN SSSVJDBUSING STOR1

PRIQTY 4000

SECQTY 130

ERASE NONUMPARTS 82

LOCKSIZE PAGE

BUFFERPOOL BP1



Partitioned table space

Partition 1 Partition 2

Page 1 Page 2 Page 3 Page 4

Table 1 Row 1

Table 1 Row 2

Table 1 Row 3

Table 1 Row 4

Table 1 Row 5

Table 1 Row 6

Table 1 Row 7

Table 1 Row 8

Table 1 Row 9

Table 1 Row 10

Table 1 Row 11

DB2 Threads



DB2 Threads

Controls Structures used by DB2 to communicate with an applicatio

program. Used to send requests to DB2, to send data from DB2 to the program, and

communicate the result of each SQL statement after it is executed.



DB2 Operating Environment

All DB2 application types can execute concurrently by sharing the same Ddatabases.

A DB2 application executing under CICS is an on-line application and us

CICS facilitates to communicate messages.

A CICS/DB2 application can access DB2 data, IMS data, and VSAM data.

The combination of DB2 with CICS performs as a full functions DB/D

system & CICS serves as the transaction manager.

Structured Query Language (SQL)



Structured Query Language (SQL)

SQL is a high level language that provides a greater degree of abstraction than

procedural languages.

It is fashioned so that the programmer can specify what data is needed but n

not specify how to retrieve it.

Used to access data in DB2 tables.

Ways of executing SQL's

Foreground

Using SQL Processor Using File Input (SPUFI)

Using Query Management Facility (QMF)

Background

By embedding them in application programs written in C, Cobol, Fortran,

Assembler, PL/1, etc.



Data Definition Language (DDL)

DDL - Data Definition Language statements to define or create the objects ofdatabase.

CREATE, ALTER, DROP

Data Manipulation Language (DML)

DML - Data Manipulation Language statements to manipulate data in tables.

SELECT, INSERT, DELETE, UPDATE

Data Control Language (DCL)

DCL - Data Control Language statements to GRANT and REVOK

authorization to user resources.



Relational concepts

Relation : A table or FileTuple : Row contains an entry for each attribute

Attributes : Columns or the characteristics thatdefine the entity

Domain:. A range of values (or Pool)

Entity : Some object about which we wish tostore information

Null : Represents an unknown/empty value Atomic Value: Smallest unit of data; theindividual data value

DB2 Database Design



DB2 Database Design

DB2 Datatypes

Null:

All datatypes include the null value. The null value is a special value that

distinct from all other values and thereby denotes the absence of a value. It

NOT the same as 0 or blanks.



Date format



Time format

DB2 Datatypes & Lengths



NOT NULL: Value must be given

NULL: If Value not given it is marked unknown

NOT NULL: If value not given DB2 fill default value

WITH DEFAULT: Numeric Becomes Zero, Character Becomes Blank, Date becomes Curr

Date, Time becomes Current Time, Timestamp becomes Current Timestamp.

If Nulls are allowed, internal storage length is increased by 1 byte



Primary & Foreign Key Concepts

Key identifies a row of data

Keys can be composed of more than one column (composite keys)

Two Types of keys

Primary Key Identifies its own row

Must be unique

Foreign Key Identifies a row of related data

Need not be unique

Tables are related only by primary & foreign keys

Table with the primary key is called parent table Table with the foreign key is called a child table or a dependent table.

Referential Integrity Rules



Referential Integrity or Relation Integrity is another elementary data integrity ru

of the relational model.

Referential Integrity defines the relationships among different columns an

tables in a relational database.

It is called referential integrity because the values in one column or set

columns refer to or must match the values in a related column or set of column

A mechanism that ensures data integrity between tables related by Primary

Foreign Keys



Insert Rules

When inserting a row with the foreign key, DB2 checks the values of the foreig

key columns against the value of the primary key columns in the parent table.

new Primary Key can be inserted as long as it is unique.

Update Rules

When updating foreign key values DB2 performs same checks as when it is inserting a row with

foreign key.

Delete RulesCascade: When a row of the parent table is deleted, any related rows in th

dependent table are also deleted.

Restrict : Rows of parent table that have dependent rows cannot be deleted

Set Null: When a row of a parent is deleted, the corresponding values of thforeign key in any dependent rows are set to null.



DDL, DML, DCL Commands

DDL Statements

Creating DB2 Objects

CREATE Statement is used to create all DB2 data objects.

• General format

CREATE Object, Object Name Option - List

Object STOGROUP | DATABASE | TABLESPACE | TABLE | VIEW | INDEX

Object Name: name of the DB2 object

Option - list: Options for the object to be defined



CREATE TABLE

This statement is used to create objects

SYNTAX : For Creating a Table

CREATE TABLE <tabname> (ColDefinitions)

PRIMARY KEY(Columns) / FOREIGN KEY

UNIQUE (Colname) (referential constraint)

CHECK (colname relational operator value)(check constraint)

[IN Database.Tablespace Name ]

CREATE TABLE

This statement is used to create objects

SYNTAX : For Creating a Table

CREATE TABLE <tabname> (ColDefinitions)

PRIMARY KEY(Columns) / FOREIGN KEY

UNIQUE (Colname) (referential constraint)

CHECK (colname relational operator value)(check constraint)

[IN Database.Tablespace Name ]

Create Tables



CREATE TABLE EMPTAB (EMPNO INTEGER(5) NOT NULL

EMPNAME CHAR(25) NOT NULL

DESIG CHAR(25) NOT NULL

SALARY DECIMAL(7,2)

DOB DATE NOT NULL

IN GSLDB.GSLTS

Create Index

CREATE UNIQUE INDEX index name ON table name (FLD 1 ASC/DESC, FLD 2ASC/DESC)

Example: CREATE UNIQUE INDEX EMPIDX ON EMPTAB (EMPNO ASC);



Create View

CREATE VIEW view name AS

SELECT FLD 1, FLD 2 ….. From table-name

WHERE condition (WITH CHECK OPTION)

Example: CREATE VIEW EMPV AS SELECT EMPNO, EMPNAME FROM EMPTAB

WHERE dept name = ‘TRG’



to Add new column

to Add Primary Key

to DROP Primary Key & Foreign Key

to Add Referential Constraints

Example:

ALTER TABLE EMPTAB ADD ADDRESS CHAR(30);

Alter Table



Notes:

Adding a primary key in a table puts the table in a

incomplete state until a unique index is created on tha

particular column. Dropping a primary key on a parent tabl

drops all references to dependent tables.

DB2 does not allow deletion of a column from a table. DB

does not allow the characteristics of the column to b

changed.



Provides effective control over the resources at require

levels, either at the row level or at the column level.

• Allows centralization / decentralization of control at require

levels.

• DB2 users may be allowed to control the use of resources

without permission/assistance of Database Administrators.

• Control over DB2 objects and data is achieved throug

GRANT and REVOKE statements.

DCL Statements



Revokes privileges from authids

General format

REVOKE authorization ON object object name FROM

authid / PUBLIC

Example:REVOKE SELECT ON TABLE EMPTAB FROM TRGE010;

Revoke



Grants privileges to Authorization Ids.

General format

GRANT authorization ON object object name to authid / PUBLIC [WITH GRANT OPTION ]

Can be executed from an application program or can be executed interactively using SPUFI

QMF

Authorization for table can be SELECT, INSERT, UPDATE, DELETE, ALTER, INDEX or ALL

For update, authorization can be given on specific columns also.

WITH GRANT OPTION allows the grantee to grant privileges to others.

Example: GRANT SELECT ON TABLE EMPTAB TO TRG010;

Grant

DML Statements



DML Statements

Insert

To insert values into the fields of a table

There are 2 types of INSERT statements.

INSERT statement with VALUES clause is used to insert a single row.

INSERT with SELECT statement is used to insert one or more rows.

General Format:

INSERT INTO tablename (col1…) VALUES (val1…);

INSERT INTO tablename (col1…) sub-select;

Example: INSERT INTO TABLE1 VALUES (005, ‘RAM’, ‘MKR’, ‘SALES’);

EMPNO Name GRPID DESIG

005 RAM MKR SALES

Example: INSERT INTO TABLE1 SELECT* FROM TABLE2;

Update



Used to change any value in a table

Changed from MKR to FIN

If WHERE clause is not used, all records are changed to ‘FIN’ GRPID

So the record changes to:

Example: UPDATE TABLE1 SET GRPID=‘MKR’ WHERE EMPNO=005;

EMPNO NAME GRPID DESIG005 RAM FIN PRG

Select



• ‘SELECT‘ statement is used to retrieve all or part of the records in a table.

‘WHERE‘ clause is used to specify the search criteria. If no criteria is specified, all the recor

are retrieved. Example: Table1

EMPNO NAME GRPID DESIG

001 JOSEPH MKR SMG

002 SAM FIN GM

003 RAJA SALES MGR



Selecting all Columns

The same answer is got even if we give SELECT EMPNO, NAME, GRPID, DESIG from TABLE

SELECT* FROM Table1 ‘*’ – to specify all columns

EMPNO NAME GRPID DESIG

001 JOSEPH MKR SMG

002 SAM FIN GM

003 RAJA SALES MGR

Selecting few Columns only



Conditional Select

WHERE clause is used to select data from only the rows that meet certain conditions. A WHERE

clause specifies a search condition that, when evaluated against a row, yields TRUE or FALSE o

UNKNOWN.

Selecting unique rows

In: To select from a list of values



Between: To select a range of values

Like: To select based on a subset of characters

Not: Negate a condition

Any

Is same as IN when given as =ANY



Is same as IN when given as =ANY

Joins

Joins are used to select data from multiple tables

Example: Table2

We are joining table 1 and table 2 to get the information of manager(s) only.

Cartesian Product



‘Cartesian product ‘ is the result of a join that does not specify matching columns.

Subquery

Used to nest SELECT statements

When one or more select statements are nested, it is referred to as sub query



To get the information for all the managers

To get the information about the 'FIN' group's manager

Union

UNION bi f i i l d f ll h i i h b h



UNION combines two sets of rows into a single set composed of all the rows in either or both o

the two original sets. The two original sets must be ‘union-compatible‘ (i.e.)

The two sets must contain the same number of columns.

Each column of the first set must be either the same data type as the corresponding column

the second set or convertible to the data type of the corresponding column of the second set.

Outer Join



When we want both matching & non - matching rows returned for one or more of the tables be

joined, we use Outer Join.

Sorting & Grouping

The ‘ORDER BY‘ clause sorts result of a query in the specified order (ascending or



The ORDER BY clause sorts result of a query in the specified order (ascending or

descending) for each column.

The ‘GROUP BY ‘ clause sorts the resultant rows to apply functions that consolidate the data

By grouping data, users can use statistical functions on a column [Example: AVG, SUM, MIN

MAX]

It does not do any sorting. For sorting, ORDER BY clause should be used.

After having grouped using the ‘GROUP BY ‘ clause to eliminate non - pertinent data we use

Having ‘ clause. The HAVING clause is to specify conditions for the GROUP BY clause.

Note: Default Order is Ascending.



Note: If there are 50 ‘MKR’, 50 ‘FIN’ & 50 ‘SALES’ records, they will be grouped together a

displayed.

Table 3:

Aggregation& Column Functions



Column functions compute from a group of rows and return a single value for a designat

column or expression.

Example: AVG, COUNT, MAX, MIN, SUM

AVG

To find the Average of a column specified or expression given as the argument

Count

To count the number of rows, use distinct keyword to count only the number of distinct values



a given column.

Max

Max function returns the largest value in the specified column or expression.

Min

Min function returns the smallest value in the specified column or expression.

Sum

This returns the accumulated total of the specified column or expression.



Delete

To delete a record or set of records or all records

General Format:

DELETE FROM table name WHERE search-condition;

If WHERE clause is not used, all records are deleted.

If WHERE clause is not used, all records are deleted.



DB2 & TSO

TSO or Timesharing Option, is one of the environments from which DB2 da

can be accessed.

TSO enables the users to interact with MVS using an on-line interface that either screen or panel driven.

The Interactive System Productivity Facility (ISPF) provides the mechanism f

communicating by panels, which is the common method for interaction betwee

TSO and application users.

Jcl to submit embedded sql000100 //MA24A JOB ,,NOTIFY=MAPLE24,MSGLEVEL=(1,1)000200 // JCLLIB ORDER=MAPLE24.DB2.PDS000300 //STEP01 EXEC PROC=DSNHCOB WSPC=500 MEM=SIMPLE user=userid To identify the library



000300 //STEP01 EXEC PROC=DSNHCOB,WSPC=500,MEM=SIMPLE user=userid To identify the library000400 //PC.SYSIN DD DISP=SHR,DSN=MAE24.DB2.PDS(&MEM) path for the source code location000410 //PC.SYSLIB DD DISP=SHR,DSN=MAE24.DB2.PDS path for the DCLGEN000420 //PC.DBRMLIB DD DISP=SHR,DSN=MAPLE24.DBRM.PDS(&MEM) path for the DBRMLIB000500 //LKED.SYSLMOD DD DISP=SHR,DSN=MAPLE24.RUNLIB.LOAD(&MEM) Path for the load module(generation)

000600 /*000700 //BIND EXEC PGM=IKJEFT01,DYNAMNBR=20,COND=(4,LT) DB2 utility000710 //STEPLIB DD DISP=SHR,DSN=DSN710.SDSNLOAD000900 //SYSTSPRT DD SYSOUT=(*)001000 //SYSTSIN DD *001100 DSN SYSTEM(DSN2) To connect to TSO001200 BIND PLAN(MAPLE24P)- plan to be created with in userid001300 MEMBER(SIMPLE)- Application member name001400 ISOLATION(CS) - cursor stability locks amount of page where Db2 resides

001500 RELEASE(C) - Close the cursor

001600 EXPLAIN(NO)- Find the optimum path001700 OWNER(MAPLE24)- userid001800 LIB('MAPLE24.DBRM.PDS')001900 RUN PROGRAM(SIMPLE) PLAN(MAPLE24P)-002000 LIB('MAPLE24.RUNLIB.LOAD')002100 /*002110 //002200 //SYSIN DD *002301 /*002310 //

002340 //

SPUFI

SPUFI (SQL Processor Using File Input) reads the SQL statements contained as a text in



sequential file, processes those statements and places the output in the output dataset specif

in the browse mode. The screen is self explanatory and the only inputs the user has to give

the input file name where the SQL statements are placed and the output file name where t

results have to be placed. SPUFI supports the online execution of SQL statements from a T

terminal.

DCLGEN CommandThe DCLGEN or Declaration Generator Command is used to produce a COBOL copybo

which contains a SQL DECLARE TABLE statement along with the WORKING-STORAGE ho

variable definitions for each column of the table. When the DCLGEN command is issued D

reads catalog to determine the structure of the table and builds the COBOL copybook.

Preparation Steps



SOURCE

DB2

PRECOMPILESQLNON

SQL

COMPILE

&

LNKEDIT

DB2

BIND

LOAD

MODPLAN

CATALOG

* *

* *

* =TIMESTAMP

Program Execution



LOADMOD

PLAN

DB2DL/I

or

VSAM

DB2

TABLESOTHER

DATA

CALLEXEC

DB2

TABLES

DB2L/I

or

VSAM

OTHER

DATA

DB2 Precompile Comments



Separates SQL from Non-SQL (Database Request Module)

Checks for errors

Does not access DB2 catalog

Can add code from Libraries

Timestamps both outputs



BIND Comments



Checks for errors, using DB2 catalog

Checks authorisation

Develops Access strategy for each statement

Stores strategies as plan (reusable without repeating bind

Pre-compilationPre-compiler Functions:

Program used: DSNHPC



Program used: DSNHPC

INPUT EMBEDDED SQL PROGRAM

OUTPUT

Modified source

DBRMLIB – Database Request Module

Other Sources needed:

DCLGEN: This produces modules that can be included in a program. It builds a COBOL copybook.

Expands the DB2 related INCLUDE statements.

Checks the SQL syntax.

Separates SQL from NON-SQL statements and places SQL statements in Database Request Mod

(DBRM)

Places TIMESTAMP in the Modified source in the DBRM member and load module.00

Compile

Program Used: IGYCRCTL



INPUT Modified Source Program; OUTPUT OBJ Module

Other Sources needed: COPYLIBS

Process:

The COPYLIB members will be expanded.

The COBOL syntax will be checked.

Places time stamp written in precompiler step in OBJ module.

Link EditProgram Used: IEWL

INPUT OBJ Module; OUTPUT Load Module

Process:

The executable load module is produced

Subprogram exists will be merged along with system libraries

Places the timestamp written from the precompiler step in the load module.

BindProgram Used: IKJEFT01

INPUT DBRM LIB produced in precompiler step



INPUT DBRM LIB produced in precompiler step

OUTPUT PLAN

Function: Reads the SQL statements from DBRMs and produces a mechanism to access da

from tables.

Parameters given while binding:

1. Owner, Qualifier

2. Action (REPLACE/ADD)

3. Isolation (CS/RR)

4. Acquire (USE/DEALLOCATE)

5. Release (COMMIT/DEALLOCATE)

6. Validate (BIND/RN)

7. Explain

8. Flag.

Owner: Name of the owner who created the PLAN

Qualifier: Name where the table reside



Action: Add or Replace the existing plan (BINDADD & BINDREPLACE)

Isolation: This determines the mode of page locking implemented by the programs as it runs.

CS – Cursor Stability:

Releases the page locks as soon as another page is accessed or an COMMIT is issue

Improves concurrency.

RR – Repeatable Read (DEFAULT):

Does not releases the page locks until a COMMIT is issued.

Acquire: This determines the mode of table space locking implemented by the program as

runs.

Use: Table space locks are acquired when the table space is accessed.



Allocate: Table space locks are acquired when the plan is allocated.

Release:

Commit : Table space locks are released at COMMIT or ROLLBACK time.

Deallocate: Table space locks are released only when the plan finishes and is deallocated.

Validate: Method of checking for the existence and validity for DB2 access tables a

authorization

Bind – Validates at Bind time; Run – Validates at run time.

Flag: Returns informational, warning, error and completion messages.

DB2 Application Programming Concepts



pp g g p

Data Base Request Module (DBRM)

DBRM is a module containing SQL statements from the source program, whi

have been extracted by the DB2 Pre-compiler.

The module is stored as a member of a partitioned data set.

The DBRM is used as input to the BIND process

Bind

Bind reads SQL statements from DBRM s and produces a method to access data as directed b



the SQL statements being bound.

It stores this access method as Plan

Two types of Binds - BIND PLAN, BIND PACKAGE

BIND PACKAGE accepts a DBRM as input and produces a SINGLE package.

A package is not executable. Packages should be bound into a plan before executing.

Output of BIND PLAN is the application plan containing the executable logic giving the access

path to DB2 data.

BIND also performs Syntax checking of SQL statements, Checking of the DB2 table and colum

catalog Information, Authorization Validation.

Compile & Link Edit• Modified source program produced by the DB2 pre-compiler is the input for COBOL compiler.

Compiled source code is given as input to Linkage editor.



Linkage editor produces the executable load module.

Appropriate DB2 host language interface module must be included in the link-edit step.

Running a DB2 Program

Program preparation steps will produce two separate physical components- DB2 Plan, Link-Edited Lo

Module.

To run an Application program containing SQL statements, the name of the Plan should be specified.

At execution time, DB2 checks for the compatibility of the Plan and the load module by comparing

TIMESTAMP.

DB2 programs can be executed in

Batch / TSO, Using Call Attach Facility, CICS

Embedded SQL

SQL statement are embedded anywhere in the application program. These are analyzed by DB2 p

compiler & replaced by equivalent statements in host language



p p y q g g

In addition to data definition/manipulation statements, SQL statements unique to application progr

coding are provided. These include support for Declaration tables, Include statements, S

Communications Area, usage of Host Variables within SQL statements & Cursor tables. DB2 application programs may be coded in COBOL, FORTRAN, PL/I and ASSEMBLY language.

Each statement is delimited i.e. each SQL is enclosed in an EXEC SQL, END-EXEC block

Data Values can be gathered from host program variables

Multiple rows of table can be accessed through a CURSOR

DB2 describes results of execution in SQLCA

End Delimiter varies by Host Language. For COBOL, it is END-EXEC.

SQL/COBOL Program Components



Working Storage:

Host program variables are defined here to hold data. These variables areferred in the SQL statements in the Procedure Division.

Procedure Division:

• SQL statements to access and manipulate data are coded here. The

statements reference DB2 tables and host program variables.

• SQL statements begin with EXEC SQL and end with END-EXEC.

SQL Communication Area:SQLCODE Field tells result of last executed SQL request

Examples: 000 Successful

+100 No more rows found



+100 No more rows found

- 530 New Foreign key value is invalid

SQLCODE field should checked after each SQL statement If SQLCODE is less than 0, an SQL error was encountered.

Including TABLE DECLARATION

• SQL provides a facility to copy source code from a library into application program, by coding INCLU

statement.

• The INCLUDE statement directs DB2 pre compiler to copy source code into the program. This functionvery similar to COPY statement in COBOL.

• INCLUDE statement is normally coded to copy DCLGEN outputs into the program’s working-stora

section. It can also be used to copy SQL or COBOL statements in the Procedure Division. However,

include code must not contain Include statements within it. I.e. nested INCLUDE.

• The general statement format is

• EXEC SQL INCLUDE source code name• END-EXEC

Host Variables, Null Indicator Variable

Host variable is an area of storage allocated by the host language and referenced in an SQ



Host variable is an area of storage allocated by the host language and referenced in an SQ

statement.

Host variables are defined and named using Host Language Syntax

For COBOL, host variables are defined in Data Division or Linkage Section

A ‘ : ‘ should precede the host variables used in embedded SQL statements

Host variables can be used as:

A host variable cannot be used for table names, column names, SQL verbs etc.

A host structure is a COBOL Group level data area consisting host variables for all colum

returned by SELECT statement. OCCURS clause cannot be used while declaring su

structures.

Notes:• For host variables not within a host structure, use COBOL level numbers 01 or 77.

• Variable character fields are defined as a 02 group level specifier, and two 49 lev



specifiers. One is the length specifier, and other is the actual data field.

• While inserting data into a variable character field, the actual number of characters instead

indicated by the length specifier.

• While retrieving data from a variable character field, the actual number of characte

returned in the data field is indicated by the length specifier.

In the above example DCLDEPT is a Host Structure containing corresponding Host variables

DEPTNO, DEPTNAME & LOCATION

Host Structure

A series of variables referenced as a unit is called a structure.

• In a COBOL 01 (group) level data structure, representing all column selected in SQL



statement. The 01 (group) level data name is prefixed by a colon

• Is coded in a SQL statement in place of elementary level fields.• Can have a maximum of two levels.

• When elementary fields have duplicate data names, they must be qualified with the relevan

structure name.

• The general coding format is: Structure Name.Field Name

Note:

• For data variable within a host structure use COBOL level numbers 02 through 48.

•Coding FILLER within a host structure makes the structure invalid.

Null Indicator VariablesIndicator variable is a 2 Byte integer S9 (4) Comp.

• Declared similar to Host variables.

• Negative value for Indicator variable means the associated column value has a NULL value.



• If a column is truncated, length of the field is returned in the Indicator variable.

• Can be declared as an array of Indicator variables. OCCURS clause can be used.

• To associate Null Indicator variable with a particular host variable for a column, code the indicator variab

immediately after the Host variable, preceded by a colon.

• Can be used along with Host variables in

• Set Clause of UPDATE Statement

• VALUES Clause of INSERT Statement

• INTO Clause of SELECT or FETCH Statement

SQLCODERegardless of whether the application program provides an SQLCA or a stand-alone variab

SQLCODE is set by DB2 after each SQL statement is executed. DB2 conforms to the ISO/AN

SQL standard as follows:



SQL standard as follows:

• If SQLCODE = 0, execution was successful.• If SQLCODE > 0, execution was successful with a warning.

• If SQLCODE < 0, execution was not successful.

• SQLCODE = 100, "no data" was found. For example, a FETCH statement returned no d

because the cursor was positioned after the last row of the result table.

Using Select - Into Clause• Only one row from the table is returned

• Example:

MODIFIED

SOURCE

MODULEb

DBRM

SOURCE

MODULE



COMPILER

COMPILER

OBJECT

MODULE

EDITOREDITOR

LOAD

MODULE

OTHER

OBJECT

OTHER

OBJECT

DB

APPLICATION

PLAN

BIND BIND

PACKAGE

BIND BIND

PRECOMPILER

PRECOMPILER

LIST OF

PACKAGE

LIST OF

PACKAGE

Cursor Processing

In the Embedded SQL application program development, if select returns mo

than one row of information then we have to use cursor’s since the progra



than one row of information then we have to use cursor’s, since the progra

cannot process all the rows at once. It can process only one row at a time.Following operations can be performed on a CURSOR

DECLARE

OPEN

FETCH

CLOSE

Cursor can return zero, one or many rows depending on the Fetch condition.



Static Embedded SQL

used when you know all the possible SQL statements that

might be written

Dynamic Embedded SQL

used when the SQL statements will be defined at

run-time (ie. they are not known in advance)



select name, ?, ?



from ?

where name = ‘jones’

select name, agefrom employee

where name = ?

Requires dynamic SQL

Can use static SQL

The syntax of the Declare cursor statement

Exec Sql



Declare cursor-name Cursor [with hold] for

Select [Distinct] col-spe[As result-col],[col-spe[As res-col]from table-name [ Where selection-cond] {[for update ofupdate-col[,update-col]..] [Order by sort-col [Asc/Des]]..}

End-Exec.

__________________________________________ _ With hold Prevents the cursor from being closed as a

result of a commit operation

Update-col

The name of the column for which you wantto enable updates

DECLARE Cursor syntax:

EXEC SQL



EXEC SQL

DECLARE cursor FOR union-expression[ ORDER BY columns) ]

FOR [ FETCH ONLY | UPDATE OF

columns) ] ]END-EXEC.

Declare Cursor

To define and identify a set of rows to be accessed.

For updating / deleting a row FOR UPDATE OF option sho



For updating / deleting a row, FOR UPDATE OF option sho

be specified.

Cursor name cannot be a Hyphenated word

Example of Cursor Declaration

WITH HOLD clause can be used with DECLARE, to retain the cursor position beyond tcommit point.

Sql Fetch statement

Exec Sql{ |



Fetch cursor-name INTO {:host-var [, :host-var]…|:host-structure }

End-Exec.

________________________________________________________________

For eg:Exec SqlFetch custcur INTO :fname, :lname

End-Exec.

Open Cursor • Activates the cursor

• Rows are retrieved and stored in the result table

f f



• Pointer is positioned before the first record

• Example

Fetch Cursor

• Moves the contents of the selected row into Program Host Variables

• Points to the next row

• Cursor must be opened explicitly before it can be fetched.

• Example

Rows are sorted by invoice in descending sequence

Declare Invcur cursor for select invcust, invno ,invtotalform invtable where invcust = :custno order by invtotald



des

__________________________________________ __ Declare custcur cursor for select fname, lname from

custtablewhere state = ‘ca’ order by 2

__________________________________________ __

Declare invcur cursor for select invno, invdate,invtot+invtax As

Total from invtable order by total

SYNTAX FOR UPDATE statement



_________________________________

Exec Sql Update {table-name | view-name}

Set col-name = {:host-var| literal|expression|null}

[,col-name = {:host-var| literal|expression|null}]…[where {search-cond [with isolation-level]|

current of cursor-name}]

End-Exec.

EXAMPLE



EXEC SQL

UPDATE tableSET column = scalar-expression[, column = scalar-expression ] …..

WHERE CURRENT OF cursorEND-EXEC.

The keyword NULL puts a null value in a column, butthis can’t be used for a column that’s defined asNOT



NOT

NULL.If a Check Constraint has been defined for a column,the value that the column is set to must satisfy theconstraint.

If the value in the sqlcode field isn’t zero it means thatthe update failed so on changes were made to thetable. Sqlerrd(3).

The CURRENT OF phrase is used to update the4current row in a cursor controlled table.

Syntax for DELETE Statement

Exec Sql

Delete from {Table-name | view-name}



Delete from {Table name | view name}

[ Where {search-con [with isolation-level ] |Current of cursor-name}]

End-Exec.

_____________________________________________

For eg:

Exec Sql

Delete from invtable where custno = ‘30000’

End-Exec.

Exec Sql

Declare custcur cursor with hold for select custno,

addr city state from invtable where invcust < ‘3330’ for



addr, city, state from invtable where invcust < 3330 for

update of custno, addr, city, stateEnd-Exec.

__________________________________________________

Changes the row at the current cursor position.

Exec Sql

update invtable set custno = :custno, addr = :addr,

city = :city, state = :state Where

current of custcur

End-Exec.

syntax for Insert with ValuesExec sql Insert into (table-name | view-name)

[ col-name [, col-name]……)]



values({ :host-var | literal | null}……..)

End-Exec. ______________________________________________

Insert into customer values( :cust-no, :custname)

If a check constraint has been defined a column the

value that’s supplied for the column must satisfy theconstraint.

Sqlcode value of -803 means that the statement failed therow to be inserted contained a duplicate value in a

column that is defined unique

Insert with a sub query

Exec sqlInsert into (table-name | view-name)



Insert into (table name | view name)

[ col-name [, col-name]……)]select-statement [with isolation-level]

End-Exec. _________________________________________

Exec sqlInsert into oldcust-table select * from

customerwhere custno < ‘30000’

End-Exec.

Updating/Deleting of Row Fetched All columns to be updated should be included in the FOR UPDATE OF Clause in DECLAR

CURSOR Statement.

WHERE CURRENT OF Clause is used in UPDATE and DELETE statements to modify t

current row



current row.

UPDATE and DELETE statement must be preceded by a FETCH statement. Examples:

Close Cursor

CLOSES the Cursor

Releases the locks held by the cursor

DB2 automatically closes cursor when program terminates

COMMIT statement also closes all the cursors

-117 The number of insert values is not the same asthe number of object columns



-304 The value inserted is out of range-305 The null value cannot be assigned to output hosvariable number because no indicator variable isspecified

-805 Program not found in the PLAN-503 A column cannot be updated because it is notidentified in the update clause of the selectstatement of the cursor

Inserted or updated value invalid because index index-name

constrains columns of table such that no 2 rows can contain

-803



The precompiler-generated timestamp x in the load module is

different from the bind timestamp y built from the DBRM

-818

The Insert, Update, Delete, DDL or Authorization StatementCannot Be Executed Because the IMS/VS Transaction Is

Inquiry Only

-817

Result of an Embedded Select Statement Is a Table of More

Than One Row, or the Result of the Sub query of a Basic

Predicate Is More Than One Value

-811

duplicate values in those columns. Rid of existing row is X’rid’

Error Handling

WHENEVER statement used to enable automatic testing of return codes for subsequent SQL

statements



Affects all subsequent SQL statements until the next WHENEVER statement

General Format

Advanced SQL Topics

Dynamic SQL



DB2 supports two types of SQL statements in an application program

- Static SQL

- Dynamic SQL

Static SQL are SQL statements embedded in a host language and bound before the progra

runs.

Dynamic SQL are SQL statements that are prepared and executed, while the programrunning.

Statements that are allowed as dynamic sql statement_____________________________________________

Statements u may be likely to use

DELETE INSERT SELECT UPDATE



DELETE,INSERT,SELECT,UPDATE.

Statements are not likely to use

ALTER,COMMERNT, COMMIT, CREATE, DROP,

EXPLAIN, GRANT, LABEL, LOCK TABLE, REVOKE,

ROLLBACK.

Cursor Processing Open, fetch, close.

Precompiler directives Declare Include Whenever.

Dynamic sql Execute Immediate Prepare .Execute Declare.

Static Vs Dynamic

For static SQL, the structure of the statement should be known beforehand, while dynamic SQ

allows complete flexibility in the structure of the statement.



Static SQL can contain host variables; Dynamic SQL cannot host variables.

Static SQL are bound beforehand, while dynamic SQL are bound at runtime and hence ru

time overhead is greater.

Static SQL select statements can have ‘INTO’ clause whereas dynamic SQL sele

statements cannot have ‘INTO’ clause.

Examples of dynamic SQL:

SPUFI, QMF

These two accept almost any SQL statement, and process and execute the SQL statemen

dynamically.

Syntax for Sql EXECUTE IMMEDIATE

_____________________________________________

Exec Sql



Exec Sql

Execute Immediate :Host-varEnd-Exec.

Host-var Cobol host variables that contains the

statement string to be translated, bound and executed.

Must contain data compatible with the DB2 varchar

data type.

Sql prepare statement

Exec Sql

P d



Prepare parpared-statement-name

[Into Sqlda-name]

From :host-var

End-Exec.

Prepared statement Symbolic name 18 characters lon

u create to identify the prepared statement .Sqlda-name The name of an sqlda where informationabout the prepared statement will be stored

Host-var Cobol host variables that contains thestatement string to be translated, bound and associat

with prepared statement.

Where a host var would not used to allowed in a static

statement. [as in from ?]



As column specifications [ as in select ?,?,?]

As both elements in a comparison [as in where ? = ?]

As both elements of an arithmetic operation

[as in where invtotal =?+?]

Categories of Dynamic SQL

Non - Select SQL Statements

Fixed - List Select Statement

Varying List Select Statement



Varying -List Select Statement

Non-Select SQL Statements

The SQL statement is stored as a string.

Can be used for insert, update or delete.

Example

Processing for aDynamic non-selecstatement thatproduces a unknowresults table

Processing for a Dynamicnon-select statementthat produces a knownresults table

Processing for aDynamic non-selectstatement executedmore than once

Processing for a Dynamic non-select statement executedonce



Declare Cursor

Prepare

Describe

Allocate storage fhost variables

Open

Fetch

close

Declare Cursor

Prepare

Open

Fetch

close

Prepare

Execute

Execute Immediate

Format non-selectstatement in avariable-length strhost variables

Format non-selectstatement in a variable-length string hostvariables

Format non-selectstatement in a variable-length string hostvariables

Format non-select statementin a variable-length stringhost variables

Example



Methods for using Non Select SQL

Prepare And Execute

Execute Immediate

May Or May Not Have Parameter Markers.



Prepare

The SQL statement is prepared and assigned a unique label.

A prepared statement can be executed several times in a program

General format

Exec Sql

Execute prepared-statement-name

[using { :host-var[: host-var] Descriptor Sqlda -name}



[using { :host-var[: host-var] Descriptor Sqlda -name}

End-Exec.

________________________________________________________

1. Symbolic name specified on the prepare statement the processed the

prepared statement u want to execute.

2. Cobol host variable whose name will be substituted for a parametermarker in the prepared sql statement.

3. Sqlda-name that contain descriptions of the host variables whose

values are to be substituted for parameter markers in the prepared

statement.

Execute Executes the SQL statement



Execute Immediate

Prepares and executes the SQL statements in one shot.

Syntax.

Fixed - List Select StatementsFixed-list implies that the number 0f columns and the datatypes of those columns are known in

advance.

Number of rows that are returned need not be known



Steps

Declare a cursor for the statement name.

Prepare the statement.

Open the cursor

Fetch rows from result table.

Close the cursor.

Example

Declare Open Fetch Close

Exec Sql

Declare cursor-name for prepared-select-name

End-Exec



End Exec.

________________________________________________________Exec Sql

Open cursor-name using {:host-var… Descriptor sqlda-name}

End-Exec.

________________________________________________________

Exec Sql

Fetch cursor-name Into {:host-var…[:host-structure]}

[using Descriptor sqlda-name]

End-Exec.

Example



Varying List Select

• Returns rows containing an unknown number of values of unknown type. Host variables to be decla

are not known in advance. May or may not have parameter markers

Steps Involved:



Include an SQLCA

• Load the input SQL statement into a data area.

• Prepare and execute the statement

• Include an SQLDA

• Declare a cursor & prepare the variable statement

• Obtain the information about the type and size of each column of the result table

• Open the cursor; Fetch a row

• Eventually close cursor and free main storage

• Handle any errors that may arise.

• SQLDA must be explicitly coded and DB2 does not provide any include file.

TABLE CONTENTS

SYSCOLUMNS Table contains one row for every column of each taband view

SYSRELS Table contains one row for every referential constra



y

SYSFOREIGNKEYS Table contains one row for every column or everyforeign key.

SYSVIEWS Table Contains One or More Row for Each View.

SYSVIEWDEPT Table records the dependencies of views on tables another views.

__________________________________________________________

SELECT NAME, COLTYPE, LENGTH FROM SYSIBM.SYSCOLUMNS

WHERE TBNAME=‘DEPT’ AND TBCREATOR=‘IKSA01’;

SQLDA Format



Performance Considerations for DB2 Programming

General Guidelines

Avoid Numeric conversions



Select only columns that are used

For single row retrieval, SELECT can be used instead of CURSOR processing.

Cursors cannot be used for Update or Delete if DECLARE CURSOR includes any of th

following :

UNION, GROUP BY, HAVING, SUB-QUERIES,DISTINCT, ORDER BY, JOINS

DECLARE CURSOR must precede any other comma (OPEN, FETCH, CLOSE) relating to

cursor.

Initialize Host variables used by the cursor before opening the cursor. Otherwise data integri

problems may arise.

Explicitly close all cursors, to increase performance.

WITH HOLD option is not available for CURSORS coded

in a CICS-DB2 program.

For Update & Delete, use Cursors to improve performance.

For non-cursor Update and Delete statements, always use primary key in the WHERE claus

Avoid SELECT * in Embedded SQL program.



p g

Filter data using WHERE clause

Use joins instead of correlated sub select statements.

INDEX Considerations

• Using an INDEX can Save a tablespace scan

Avoid a sort. DB2 decides on use of an INDEX.

A table can have more than one Index on different Columns.

Access paths :Tablespace Scan

Clustered Index Scan, Non-clustered Index Scan.

DB2 & CICS

CICS or ‘Customer Information Control System’ is a database/data communication cont

system. We can access DB2 data from CICS programs. When DB2 data is accessed fr

CICS, multiple threads can be active simultaneously, enabling concurrent access to a D



, p y, g

subsystem by multiple users of a CICS region. A mechanism called CICS Attachment Fac

connects CICS with DB2. Using this facility, each CICS region can be connected to only one D

subsystem at a time. Each subsystem can, however, to be connected to more than one CI

region at a time.

CICS provides an interface to DB2, but DB2 requires its own region independent of the CI

region. Both CICS and DB2 require its own unique regions under the OS. CICS applicat

programs can be issue a set of commands for SQL services in order to access the D

database.

Locks

DB2 allow more than one application to access the same data at essentially same time. This

known as concurrency . To control such undesirable results such as lost updates, access

uncommitted data and unrepeatable reads, concurrency must be controlled. DB2 uses lock



uncommitted data and unrepeatable reads, concurrency must be controlled. DB2 uses lock

control concurrency.

DB2 locks can be compared in four basic aspects: object, size, duration, and mode.

Object of lock is the resource being locked.

Size of lock can be page, table or tablespace

Duration of lock is the length of time the lock is held. It varies according to when the lock

acquired and released. This is controlled by bind options ACQUIRE, RELEASE and ISOLATIO

Mode of lock tells what access to the locked object is permitted to the lock owner and to a

concurrent application processes.

Page Lock modes:

S (SHARE) The lock owner and any concurrent processes can read but not

change the locked page. Concurrent processes can acquire S or U locks on

the page.



U (UPDATE) The lock owner can read but not change the locked page; howev

the owner can promote the lock to an X lock and then can change the page

Processes concurrent with the U lock can acquire S locks and read the pag

but no concurrent processes can acquire a U lock.

X (EXCLUSIVE) The lock owner can read or change the locked page.

Concurrent processes cannot acquire any lock on the page nor can they

access the locked page.

Effects of DB2 locks:

The IMS resource lock manager (IRLM) is responsible for managing

requests for locks and controlling access to DB2 databases.



Suspension: The IRLM suspends an application process if it requests a lo

on an object that is already owned by another application process and cann

be shared. The suspended process is said to be “Waiting” for the lock. T

process resumes running when the lock is available.

Timeout : Timeout occurs when the application process is suspended for long

than a preset interval. DB2 reports a timeout by returning a SQLCODE of –9

or –913 to the process.

Deadlock: A deadlock occurs when 2 or more application processes each hold lock

resources that the others need and without which they cannot proceed. After the end of t

preset time interval, DB2 can rollback the current unit of work for one of the processes,

request the process to terminate. That frees the locks and allows the remaining processes



continue.

ACQUIRE and RELEASE options:

These options of BIND or REBIND are used to specify when DB2 is to lock the tables

tablespaces and when to release the locks.

ACQUIRE (ALLOCATE)/RELEASE (DEALLOCATE)

This option avoids deadlocks by locking your resource at the beginning. Use this option

processing efficiency is more important than concurrency.

All tables or tablespaces are locked when the plan is allocated and released only when the p

is terminated. This option reduces concurrency.

ACQUIRE (USE)/RELEASE (DEALLOCATE):

The table or tablespace is locked only when it is needed while running. All tables a

tablespaces are unlocked only when the plan terminates.



ACQUIRE(USE)/RELEASE(COMMIT) :

This is the default option & provides greater concurrency. A table or tablespace is locked o

when needed. The lock is released when a SQL COMMIT or ROLLBACK statement is issued

when the application process terminates.

This option can increase the frequency of deadlocks

ACQUIRE(ALLOCATE)/RELEASE(COMMIT)

is not allowed.

ISOLATION option.

This option on BIND or REBIND helps DB2 release S or U page locks as soon as possible. The ISOLATION opt

does not apply to changed data. All changed data remains locked at least until the next commit point. T

ISOLATION option can be either CS or RR



CURSOR STABILITY (CS)

For read only processing, the page lock is held only while the cursor is positioned on that page. When the curs

moves to another page, that lock is released. The application is protected from concurrent updates or deletion

the row it is currently processing.

REPEATABLE READ(RR)

Page locks are held at least until the next commit point. With this option, if the application process returns to

same page and reads the same row again, the data cannot be changed. The application process is assured t

SQL SELECT statements it issues are repeatable.

Use Repeatable Read when your application has to retrieve the same rows several times.

APPENDIX

Common SQL CODES



Limits Imposed by DB2

Identifier Length Limits



Numeric Limits

String Length Limits



Date Time Limits

DB2 Limits



Exercises

Code and execute CREATE statements to create EMPLOYEE & DEPT Tables.

Table Specifications



Customer Details

Account Details



Using the Basic Select:

Display all the rows and columns from Customer table.

• Display Acc_no,Acc_Type, Name, Balance from Customer table

• List all the information for any account type where Rate_o_int is unknown

• Display the Acc_no, Name , Acc_Type, DOB and Balance of all Customers who have le

th 4000 B l S t th lt b



than 4000 Balance. Sort the results by name.

• List the Accounttypes & MinBal where Rate_o_int is unknown.

• Show Acc_no, name, address and phone no of customers whose accounttype is either CA

SB.

• Produce a list of customers whose name begins with “V”. Sort the list by name.

• Display name, Acc_type & balance. for customers with a balance greater than 10,000.

• Produce a list of customers whose Balance is < 3,000. List the output in descending order

of balance.

Using the Complete Select Statement

Display the sum of all balances along with the company average balance balance, minimum a

maximum balance

• Which customer name comes first alphabetically?

• How many different acctypes do customers have?

Sho the a erage balance for each acc no



• Show the average balance for each acc_no.

• List the average balance for each acc_type where the average balance is greater th

50,00.00

• Display name, Acc_no and acc_type name in all account types whose Acc_type begins w

C.

• Show the average balance for men and the average balance for women for each acc_typ

Identify the acc_type by name. Order the results by descending balances within accou

details.

• Produce a report that gives the no. of customers and total balance for acc_types that be

with “C”, “S” or “F” . List the results in order by acc_type balance.

Using Select Statement with Subqueries

Show the name and acc_type of customers in all phone nos where phone no includes “472”

• Display name and acc_type of customers in all phone nos where phone no includes “472”

• List each acc_type that has an average balance less than banks average balance.

• Display list of all acc_no of female customers and male customers in all acc_type whe

acc type includes "SB"



acc_type includes "SB"

• Write a program to insert data into the customer and account details table after accepting t

required data from the terminal

• Write a program to list all the customersin the bank and write the result to a sequential file

• Write a program to update the account details table by accepting the acc type from t

terminal

Source Program

Modified SourceNon-SQL

DB2 Precompileror Host-

LanguageCompiler

SQL



Object Program

Link Edit

Compilation

Load Module

DBRM

Bind PackageDB2 Catalog Bind Plan

Plan

Source Program

Modified SourceNon-SQL

DB2 Precompileror Host-

LanguageCompiler

SQL



Object Program

Link Edit

Compilation

Load Module

DBRM

Bind PackageDB2 Catalog Bind Plan

Plan

db2 application modified

Documents