COBOL_Training_Class-11.ppsx

7/27/2019 COBOL_Training_Class-11.ppsx

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IBM Mainframes

COBOL Training Class-12



DataSets

Dataset: A named collection of data in an IBM

mainframe operating system. A data set in an IBM

mainframe is the equivalent of a file in other

operating systems

A dataset is typically stored on Direct Access Storage

Disk (DASD or magnetic tape .

!hese Dataset are of t"o types: #DS (#artitioned Dataset

#S (#hysical Sequential Dataset



Partitioned Data Set & Physical Sequential Dataset

PDS or Partitioned Data Set is a dataset containing multiple partition$s

each of "hich may contain a members

Members are %&B&' #rograms )%' #rograms 'oad Modules etc.

!he #artitioned Data Set can only allocate on a single volume "ith the

ma*imum si+e of ,--, tracks.

PS or Physical Sequential Data Set is a dataset that contains records

Records like employee details customer details etc.



DASD & Main-Memory

Direct Access Storage Disk ( DASD ) Mainframes /ard Disk

"hich stores the physical data

DASD

UNITS ( SYSDA & SYSADA)

!"U#$S

DATA S$TS #$#%$RSR$'"RDS

#ain#eory :

Mainframes temporary space used 0y varia0les of an

application program.



Steps to follow

*+ Allocation: !he files used in the program should 0e declared1specified in

2I'34%&5!6&' paragraph "ith4in I5#7!4&7!#7! S3%!I&5 of

358I6&53M5! DI8ISI&5.

,+ De-inition. !he 6ecord layout of the file and its attri0utes are defined in

the 2D #A6A96A#/ "ith4in 2I'3 S3%!I&5 of DA!A DI8ISI&5..+ "/en: Dataset is connected1readied to your program using &#35

statement. !he mode of &#35 decides the operation allo"ed and the

initial pointer in the dataset.

0+ Process: #rocess the file as per requirement using the I4& statements

12I'3 836BS provided 0y %&B&'. (63AD 6I!3 636I!3 and

D3'3!3

1+ 'lose: After the processing close the file to disconnect it from the

program.



Enironment !iision

Define the file in 2I'34%&5!6&' #aragraph of I5#7!4&7!#7!

S3%!I&5 "ith in 358I6&5M35! DI8ISI&5.

S$$'T Statement is used to define a file.

358I6&5M35! DI8ISI&5. I5#7!4&7!#7! S3%!I&5.

2I'34%&5!6&'.

S3'3%! "2I'A3I$NA#$ ASSI95 !& DD5AM3

&69A5I;A!I&5 IS S3<735!IA'

A%%3SS M&D3 IS S3<735!IA'2I'3 S!A!7S IS S4S!A!7S.

&rgani+ation and Access mode is optional for a #S file the default is

sequential itself



"oints To #ote

Nu4er o- S$$'T statements specifies num0er of files

used in a program.

'ogical file name is used through out the program e*ecution.

Must not e*ceed = characters.

'ike 3M#2I'3 %7S!2I'3 I542I'3 &7!2I'3 etc.

DD5AM3 Acts as a link 0et"een logical and physical file

name "hich is used in the e*ecution )%'.

Must 5ot 3*ceed = %haracters.

'ike 3M#DD %7S!DD I54DD &7!4DD 3!%.



Organi$ation an! A%%ess Mo!e

"rgani5ation : !he "ay in "hich records are arranged in the file.

6ays o- organi5ation 7

Sequential &ne record after other

Inde8ed Based on a inde* key value ( 8SAM

Relati9e Based on a relative record num0er ( 8SAM

Access ode : !he "ay in "hich records can 0e accessed ( 63!I63D

from a file.

Access ode are 7

Sequential &ne after other record only till end of the file

Rando Access directly a record from the file

Dynaic Both direct and sequential com0ined



ile Stat's Co!e

It is a t:o4yte "orking storage item. !he first 0yte denotes the

general category "hereas second 0yte denotes the particular type of

error message under that category.

0 Successful OPEN/READ/WRITE Operation

>> Successful completion

10 When AT END conition fails ?> Sequential 63AD is attempted

a-ter the end o- -ile is reached

@> >

@? @@ @ @C > @ all these are related to 8SAM.

> &pening 3rror 'ike.. mostly

C> 'ogical 3rror in programs



DATA DI(ISIO#

2ile has to 0e descri0ed in 2D #aragraph of 2I'3 S3%!I&5 "ith in

DA!A DI8ISI&5.

2ile section should 0e the first section if coded.

Synta*:

DA!A DI8ISI&5.

2I'3 S3%!I&5.

2D '&9I%A'42I'35AM3

'AB3' 63%&6DS A63 S!A5DA6D1&MMI!3D.

>? 63%&6D4'AE&7!.>- F.. 1 %&#E %&#EB&&G45AM3.

Instead of record layout specifying here "e mostly use %&#EB&&G .



Open an! Close

Any file operated in an application program need to 0e opened

first and later on closed after the task completion .

Synta* :

&#35 &#35I594M&D3 2I'3?H2I'3@.

%'&S3 2I'3?H2I'3@.



ile Opening mo!es

e have C type of opening modes.

!hey are :

INPUT Mode :4 %an perform only read

"ut/ut Mode :4 %an perform only "rite

I" Mode :4 %an perform read and re"rite

$8tend Mode:4 %an append a ne" record to e*isting file



ile Operation & ile (er)s

!o perform any operation on file "e use one file ver0 "hich are listed 0elo"

3ile 9er4 Action "/ening ode

&#35 %onnect to file 444

%'&S3 6elease the file 444

63AD 6etrieves a record I5#7!

6I!3 Adds a ne" record &7!#7!

636I!3 7pdate an e*isting record I4&

D3'3!3 Delete$s a record I4&



*EAD (er)

63AD ver0 reads a single record at a time. 6ecord fetch 0y read statement

"ill 0e moved into the record layout defined at 2D "ithin 2I'34

S3%!I&5. 2ile must 0e opened in I5#7! 1 I4& Mode

Synta* ?. !o read only one record

63AD 3I$NA#$ HI5!& S463%&6D4'AE&7!

Synta* @. !o read till end of the file sequentially

63AD 3I$NA#$

A! 35D

S!A!3M35! 5&! A! 35D

S!A!3M35!

35D463AD.



+*ITE (er)

6RIT$ 836B is used to "rite a ne" record into the file. 2ile must

0e opened in "UTPUT Mode.

!he data has to 0e moved into the record layout 0efore making a "rite

statement.

Synta* :

6I!3 63%&6D4'AE&7!.

63%&6D 'AE&7! defined in 2I'34S3%!I&5 along "ith 2D

6I!3 63%&6D4'AE&7! 26&M S496&7#45AM3.

S &6GI594S!&6A93 S3%!I&5 data4area



*E+*ITE (er)

636I!3 836B updates a specific record "hich is already e*ists

in the file. 2ile must 0e opened in I" Mode.

!he updated data has to 0e moved into the record layout 0efore

making a re"rite statement.

Synta* :

R$6RIT$ 63%&6D4'AE&7!.



DELETE (er)

Delete ver0 delete;s a record from the file.

6ecord present in #S 2I'3 cannot 4e deleted instead "e move space

to remove a record from the file.

Synta* :

D$$T$ 2I'35AM3.

Deletes only one record not the file.



Sample "rograms

In Practical



T,an .o'

Documents

COBOL_Training_Class-11.ppsx