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WORK WITH LOGICAL-FILEDay 4

Logical Files:

Overview:

This module enables the student to understand the concept of Logical File.

Outline:Topics covered,

Logical le creation

Concept of Keyed !e"uential access

Commands related to les

Obective:#y the end of this module, the student should be able to$

Create a Logical le

%nderstand the part of Logical les. Commands related to les.

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Logical File:+ logical le is provide access the data stored in one or more physical les. The featuresuni"ue to logical les include the folloing$

). Logical les do not contain data.-. +ccess one or more physical les in an arrival se"uence or in any single or multiple

eld 'ey/ value order.0. + physical le may be processed by any number of logical les.4. To or more logical les may share the same access path.1. 2mit and select criteria may be specied in a logical le to process only the

re"uired physical le data.3. + logical le may include multiple record formats. ach format hoever must relate

to one or more physical les and include at least one 'ey eld.5. 2ne logical le ith multiple record formats may process only the re"uired physical

le data.6. + logical le ith multiple record formats may be used to process the data from

more than one physical le. The le record formats accessed may be of di7erentlengths.

8 During processing a physical le9s eld attributes may be changed by a logical le.

:oever, the data stored in the physical le not be modied.

Logical les may be specied as either nonoin or oin. + non;oin logical le processeseach record individually from one or more physical les.

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:o to create simple logical le Create student pf le as discussed above. Li'e physicalle create logical le as shon belo. (ress *F+,

I# #E.T %TE/ 0O1 HA2E TO WRITE %O1RCE T0/E A% *LF, %O1RCE (E(3ER 4

Start Source Entry Utility (STRSEU)

Type choices, press Enter.

Source file . . . . . . . . . . > MYDDS Name, !R"

#i$rary . . . . . . . .> !%&'U&'D Name, #%#, UR#%, !R"

Source mem$er . . . . . . . . . #STUDENT Name, !R", SE#ET

Source type . . . . . . . . . . #* Name, S+ME, %+S, %+S!...

Tet -escription/ . . . . . . . -#01+# *#E *0R STUDENT/

%ottom

*23Eit *43!rompt *53Refresh *'63ancel *'237o8 to use this isplay

*643More 9eys

PRESS ENTER SO THAT YOU GET THE FOLLOWING SCREEN

olumns . . . : ' ;' Eit S7EET #STUDENT

*MT #* .....+..........T.Name.#enTDp%......*unctions

%e?innin? of ata @@@@@@@

@@@@@@@

@@@@@@@

@@@@@@@

@@@@@@@

@@@@@@@

@@@@@@@

@@@@@@@

@@@@@@@

@@@@@@@

@@@@@@@

@@@@@@@

@@@@@@@

@@@@@@@

@@@@@@@ En of ata

*23Eit *43!rompt *53Refresh *A3RetrieBe *'&3ursor *''3To??le

*'C3Repeat fin *';3Repeat chan?e *643More 9eys

Mem$er #STUDENT ae tofile !N&'U&'D

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olumns . . . : ' ;' Eit !%&'U&'D #STUDENT


%e?innin? of ata

@@@@@@@

En of ata

!rompt type . . . #* Seuence num$er . . . FFFFF

Name Data Decimal

Type Name #en?th Type !ositions Use

*unctions

*23Eit *43!rompt *53Refresh *''3!reBious recor *'63ancel *623Select prompt

*643More 9eys

Enter re5erence 6le using */FILE&FILE #A(E), 5unction 7e! as well as recor85or9at na9e as sown below :



%e?innin? of ata

&&&'.&& + R SR !*#E(STUDENT)

En of ata

!rompt type . . . #* Seuence num$er . . . &&&'.&&

Name Data Decimal


R SR

*unctions

!*#E(STUDENT)

*23Eit *43!rompt *53Refresh *''3!reBious recor

*'63ancel *623Select prompt *643More 9eys

Enter 7e! 6el8 o5 re5erre8 "!sical 6le :

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File name usin (F=L/

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%e?innin? of ata

&&&'.&& + R SR !*#E(STUDENT)

&&&6.&& G R0##

En of ata

!rompt type . . . #* Seuence num$er . . . &&&6.&&

Name Type Name #en?th Type Decimal !ositions Use

G R0##

*unctions



/ress F; an8 use o"tion

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%e?innin? of ata

&&&'.&& + R RSTUDENT !*#E(STUDENT)

&&&6.&& + R0##

&&&2.&& + SN+ME

&&&4.&& + 0RS

&&&5.&& + G R0##

En of ata



H 0!YR17T %M 0R!. 'AI', 6&&6.

Above logical 6le sows 5ollowing out"ut:

1se R1#@R0 co99an8 on co99an8 "ro9"t to see te out"ut

Display Report

Report 8ith . . . . . : 'A

!osition to line . . . . . Shift to column . . . . . .

#ine ........'........

R0## SN+ME 0RS

&&&&&' '&' sneha BB

&&&&&6 '&6 ramesh hh

&&&&&2 '&2 titu iii

&&&&&4 '&4 rahul +S4&&

En of report

%ottom

*23Eit *'63ancel *'A3#eft *6&3Ri?ht *6'3Split

Also !ou are able to 8e6ne 9ulti5or9at logical 6le as sown below:

olumns . . . : ' ;' Eit !%&'U&'S #STUDENT


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%e?innin? of ata

&&&'.&& + R RS !*#E(STUDENT)

&&&6.&& + R0##

&&&2.&& + SN+ME

&&&4.&& + 0RS

&&&5.&& + G R0##

&&&5.&'

&&&C.&& + R R0RS !*#E(0RS)

&&&;.&& + G D

En of ata



HOW TO 1%E COLH'G *TE.T, KBW:

Colu9ns : < < E8it /3>

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#ine ........'........6.

R0## N0 SN+ME 0RS

&&&&&' '&' sneha BB

&&&&&6 '&6 ramesh hh

&&&&&2 '&2 titu iii

&&&&&4 '&4 rahul +S4&&

En of report

%ottom


The following keywords are select and omit level keywords:1.COMP 2.RANGE 3. VALUE

HOU TO USE ABOVE KEYWORD WITH SELECT & OMIT:olumns . . . : ' ;' Eit !%&'U&'D #STUDENT


%e?innin? of ata

&&&'.&& + R RS !*#E(STUDENT)

&&&6.&& + R0## 0#7D1(-R0## N0/)

&&&2.&& + N+ME TEJT(-STUDENT DET+#/)

&&&4.&& + 0RS

&&&4.&' + G R0##

&&&5.&& + S R0## 0M!(1T '&6)

En of ata

!rompt type . . . #* Seuence num$er . . . &&&4.&'

Name Data Decimal


S R0##

*unctions

0M!(1T '&6)



+bove eld shos the folloing output$


Ltd.

F2?!LCTK*B

F2? T: !LCTD

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Display Report

Report 8ith . . . . . : 6'


#ine ........'........6.

R0## N0 SN+ME 0RS

&&&&&' '&2 titu iii&&&&&6 '&4 rahul +S4&&

En of report

%ottom


Like that we are able to use range and value keyword with logical file. Now use of omits keyword

with logical file.


*MT #*.....+..........T.Name.#enTDp%......*unctions

%e?innin? of ata

&&&'.&& + R RS !*#E(STUDENT)

&&&6.&& + R0## 0#7D1(-R0## N0/)&&&2.&& + N+ME TEJT(-STUDENT DET+#/)

&&&4.&& + 0RS

&&&4.&' + G R0##

&&&5.&& + 0 R0## 0M!(1T '&6)

En of ata

*23Eit *43!rompt *53Refresh *A3RetrieBe *'&3ursor *''3To??le*'C3Repeat fin *';3Repeat chan?e *643More 9eys

H 0!YR17T %M 0R!. 'AI', 6&&6.

Note:Omit keyword is always used with DYNSLT to omit the value. This is logical fle levelkeyword.

Out"ut o5 above *o9it, 7e!wor8 is as sown below see it using R1#@R0co99an8 on co99an8 line:


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Display Report

Report 8ith . . . . . : 6'


#ine ........'........6.

R0## N0 SN+ME 0RS

&&&&&' '&& +% +S4&&

&&&&&6 '&' sneha BB

En of report

%ottom


0ou can use tis 7Bw on one 6el8 one 6le as sown below



%e?innin? of ata

&&&'.&& + R RS !*#E(STUDENT)

&&&6.&& + R0## 0#7D1(-R0## N0/)

&&&2.&& + SN+ME TEJT(-STUDENT DET+#/)&&&4.&& + 0RS

&&&5.&& + G R0##

&&&C.&& + 0 R0## 0M!(E= '&6)

&&&;.&& + S R0## 0M!(1T '&&)

En of ata



H 0!YR17T %M 0R!. 'AI', 6&&6.

0UT!UT 0* T7S 0M!+RS0N S

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Display Report

Report 8ith . . . . . : 6'


#ine ........'........6.

R0## N0 SN+ME 0RS

&&&&&' '&' SNE7+ ""

&&&&&6 '&2 titu iii

En of report

%ottom *23Eit *'63ancel *'A3#eft *6&3Ri?ht *6'3Split

1se o5 value 7e!wor8 :

columns . . . : ' ;' Eit !%&'U&'D #STUDENT *MT

#* .....+..........T.Name.#enTDp%......*unctions

%e?innin? of ata

&&&'.&& + R RS !*#E(STUDENT)

&&&6.&& + R0## 0#7D1(-R0## N0/)&&&2.&& + N+ME TEJT(-STUDENT DET+#/)

&&&4.&& + 0RS

&&&4.&' + G R0##

&&&C.&& + 0 R0## "+#UES('&6)

&&&;.&& + S R0## 0M!(1T '&&)

En of ata



2utput of this 'eyord is here roll number having value )E- gets omitted.

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Display Report

Report 8ith . . . . . : 6'!osition to line . . . . . Shift to column . . . . . .

#ine ........'........6.

R0## N0 SN+ME 0RS

&&&&&' '&' sneha BB

&&&&&6 '&2 titu iii

En of report

%ottom


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@uestions relate8 to above session:

;

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#o Fiel8 #a9e Length Data Type Description) E(/#O 1,E ( mployee number- E(/#( -E + mployee @ame0 E(/A'' -E + mployee +ddress4 E(/%AL 5,- ( mployee !alary1 E(/'/T )E + mployee Dept.

). +dd the primary 'ey constraint %sing +DD(FC!T/ named C!T) on (F %*L.-. +dd records using DF% and observe the e7ect on addition of duplicate records.0. ?emove the constraint C!T) using the command ?JG(FC!T.4. +dd the %ni"ue 'ey constraint %sing +DD(FC!T/ named C!T- on (F %*L.1. +dd records using DF% and observe the e7ect on addition of duplicate records.3. ?emove the constraint C!T- using the command ?JG(FC!T.

;;D : Create a physical le EMPLDith the folloing DD!

#o Fiel8 #a9e Lengt 'ata T!"e 'escri"tion) E(/#O 1,E ( mployee @o- E(/'/T )E + mployee @ame

). +dd referential constraint C!T0 on the (F J(LD giving parent le name as %*L.Try to delete a dependent record from %*LD. ?emove the constraint CST"usingthe command ?JG(FC!T.

-. +dd a physical le trigger on %*LD ith trigger time as #F2?, event as=@!?T and (rogram @ame as Test. 2b;ect of this program ill be copied into yourlibrary/.

0. @ame the to types of logical les. :o do they di7er in processing logic

4. Bhen a logical le references one or more physical les, hat is automatically builtby each logical le to control processing

1. Bhat is the function of a (F=L 'eyord

3. :o many physical les ill be accessed by the non;oin logical e

5. Bhat is he function of the F2?J+T 'eyord

6. Bhat is function of the D!C@D 'eyord

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