db2 trianing class 04

8/21/2019 Db2 Trianing Class 04

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COBOL-DB2 Program

DB2 Training Class 04


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Required Steps

Write a COBOL + DB2 programCompile the COBOL + DB2 program

Execute the program.


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Required Copyboos

SQLCAcopy book

Hostvariable/DCLGENcopybook

Application program containing SL !tatement !houl" ha#e SLCA

copybook. SLCA copybook i! a collection o$ #ariable! that areup"ate" $or e#ery SL !tatement.

%hi! copybook i! o$ 136byte! in length.

Contain! mo!t important #ariable like SLCODE& SLE''D

SQLCODEcontain the !tatu! co"e a$ter e#ery Execution o$ SL

!tatement (ho!e picture clau!e i! S9(9)COMP-3.

SQLERRDi! an occur! "ata item in (hich the * occurrence contain!

the number o$ e$$ecte" ro(! by a gi#en uery i.e. SQLERRD(3).


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!ost "ariable

%he!e are #ariable "e$ine" in the ostla!"#a"eto u!e in

application program.

,o!t -ariable are the only mean! o$ mo#ing "ata $rom an"

to DB2 table!

We u!e DCLGEN tool to pro"uce ho!t #ariable are the

!ame a! the column o$ the table!

We nee" to co"e ho!t #ariable! (ith in the SL !tatement

but !houl" be prece"e" by $olo!(%&'


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#mbedded S$L

All the SL relate" !tatement !houl" be co"e"embe""e" in

bet(een

E/ECSL 0 E1DE/EC.

Both SLCA an" ho!t #ariable !houl" be co"e" in bet(een

E/EC SL an" E1DE/EC (ith 31CL4DE Statement.

E/ECSL E/ECSL

31CL4DE SLCA 31CL4DE DCL5E1

E1DE/EC. E1DE/EC.


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#mbedded S$L Statement

E/ECSL 31SE'% 31%O E678%AB9E1O&E1A6E)

-AL4ES9:,SE1O&:,SE1A6E)

E1DE/EC.

E/ECSL SELEC% E1O&E1A6E 31%O :,SE1O&:,SE1A6E;'O6 E678%AB W,E'E E1O

E1DE/EC.

E/ECSL 47DA%E E678%AB SE% E1A6E


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Program Preparation

We nee" to $ollo( $e( !tep!

7recompile

Compile0 link

Bin"

7ackage9B31D7AC?A5E)

7lan9B31D7LA1)


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Pre%ompile

Searche!all the SL !tatement! an" inclu"e member! an"

comment! out e#ery SL !tatement! in the program

%he SL !tatement are replace"by a call!tatement along

(ith the parameter!

All SL !tatement! are extracte"an" put in a DB'6

Both SLCA 0 DCL5E1 copybook! are expan"e" in the

pre compile proce!! only.

3t al!o a!!ign a time !tamp to the mo"i$ie" co"e an" DB'6

member.


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Compile and Lin

6o"i$ie" COBOL co"e output i! then compile"

Compile" co"e i! then link e"ite" to an Executable

loa" mo"ule


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B&'D Pro%ess

A type o$ compiler $or SL !tatement u!ing a pre (ritten

program i.e. 3?@E;%=>

3t rea"! the SL !tatement $rom the DB'6 an" pro"uce! a

mechani!m to acce!! "ata a! "irecte" by the SL !tatement

3n thi! bin" proce!! it check! the !yntax& check! $or the

correctne!! o$ the table 0 column! "e$inition! again!t the

catalog in$ormation an" per$orm authentication #ali"ation

%he output o$ the bin" proce!! can be a package or a plan


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Pa%age ( its )d"antage

7ackage i! boun" $orm o$ SL !tatement

Ava!ta"es:

'e"uce" bin" time

Can !peci$y bin" operation in the programmer le#el

7ro#i"e remote "ata acce!!


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PL)'

7ackage i! not Executable (here a! plan i! Executable

An application plan contain one or both o$ the $ollo(ing

element!

A li!t o$ package name!

%he boun" $orm o$ SL !tatement taken $rom one or more

DB'6

E#ery DB2 application reuire! an application plan

7lan! are create" u!ing the DB2 !ub comman" B31D 7LA1


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Bind Parameters


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Bind Parameters

SS%S31 DD

DS1 SS%E69DB5)

B31D 7AC?A5E9;SS%SO7?) 6E6BE'9DB'66E6)

OW1E'9;SS>) 4AL3;3E'9;SS>)

-AL3DA%E9B31D) 3SOLA%3O19CS) 'ELEASE9CO663%) AC%3O19'E7LACE)

E/7LA3191O)

E1D

SS%S31 DD

DS1 SS%E69DB5)

B31D 7LA19;SS>7L) 7?L3S%9;SS%SO7?.)


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Bind Parameters

7?L3S%: 7?L3S% i! a bin" parameter o$ bin" plan. 7ackage! to be

connecte" (ith plan are name" here.

AC%3O19ADD'E7LACE) package or plan i! a"" or replace". "e$ault

i! 'E7LACE.

AC43'EA1D 'ELEASE:

AC43'E94SEALLOCA%Elock! table an" table !pace on u!e

'ELEASE9CO663%DEALLOCA%E) relea!e (hen the plan

terminate!

SLE''O'91O7AC?A5ECO1%314E) it !ay! (eather to create the

package in ca!e o$ !l error

E/7LA319ES1O) loa"! the acce!! path !electe" by the optimFerin

plan8table. no i! "e$ault


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&solation Le"els

Lost *+ates% %hi! e#ent occur! (hen t(o

tran!action! rea" the !ame "ata& both attempt to up"ate

that "ata& an" one o$ the up"ate! i! lo!t.

Dirt, Reas% %hi! e#ent occur! (hen a tran!action

rea"! "ata that ha! not yet been committe".

No!re+eatable Reas% %hi! e#ent occur! (hen a

tran!action rea"! the !ame ro( o$ "ata t(ice& but get!

"i$$erent re!ult! each time

Pa!tos'%hi! e#ent occur! (hen a ro( o$ "ata

matche! !ome !earch criteria but initially i! not !een.


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&solation le"els

Re+eatable ReaRea Stabilit,

C#rsor Stabilit,

*!$oitte Rea


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.e Re+eatable Rea &solation Le"el

%he 'epeatable 'ea" i!olation le#el i! the mo!t re!tricti#e

i!olation le#el a#ailable.

When thi! i!olation le#el i! u!e"& e#ery ro( that i! re$erence"

in any manner by the i!olate" tran!action i! Glocke"G $or the"uration o$ that tran!action.

%hu!& i$ a tran!action !can! >&=== ro(! in or"er to retrie#e >=&

lock! are acuire" an" hel" on all >&=== ro(! !canne"Hnot

Iu!t on the >= ro(! retrie#e".


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T*e Read Stability &solation Le"el

(hen the 'ea" Stability i!olation le#el i! u!e"& only ro(! thatare actually retrie#e" by a !ingle tran!action are locke" $or the

"uration o$ that tran!action.

phantom!& ho(e#er& can an" may be !een but becau!e o$ $e(er

lock! are acuire"& more tran!action! can run concurrently.

i$ a tran!action !can! >&=== ro(! in or"er to retrie#e >=& lock!

are only acuire" an" hel" on the >= ro(! retrie#e"Hnot on all>&=== ro(! !canne".


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T*e Cursor Stability &solation Le"el

When the Cur!or Stability i!olation le#el i! u!e"& only the ro(

that i! currently being re$erence" by a cur!or i! locke". %he

lock acuire" remain! in e$$ect until the cur!or i! repo!itione"

or until the i!olating tran!action terminate!.

3$ the cur!or i! repo!itione"& the lock being hel" on the la!t ro(

rea" i! relea!e" an" a ne( lock i! acuire" $or the ro( the

cur!or i! no( po!itione" on..

1on repeatable rea"! an" phantom!& on the other han"& can an"may be !een.


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T*e +n%ommitted Read &solationLe"el

%he uncommitte" rea" i!olation le#el i! the lea!t intru!i#ei!olation le#el pro#i"e".

3n $act& (hen the uncommitte" rea" i!olation le#el i! u!e"& ro(!

that are retrie#e" by a !ingle tran!action are only locke" i$

another tran!action attempt! to "rop or alter the table $rom (hich

the ro(! (ere retrie#e". Becau!e ro(! o$ten remain unlocke"

When thi! i!olation le#el i! u!e"& "irty rea"!& nonrepeatable

rea"!& an" phantom! can occur.

%he uncommitte" rea" i!olation le#el i! commonly u!e" $or

tran!action! that acce!! rea"only table!#ie(! or tran!action!

that execute uerie! on (hich uncommitte" "ata $rom other

tran!action! (ill ha#e no a"#er!e a$$ect


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T*an ,ou

db2 trianing class 04

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