IBM Natural Interview Questions And Answers

Normally in JCLs calling natural program, data is passed
using some control cards. In the natural program, the data
is received in the same order using INPUT statement similar
to STACK processing.

Data definition in Natural is done using following:

DEFINE DATA
1 #VARIABLE1 (A10) /* Alphabetic variable of length 10
..
..
END-DEFINE

ESCAPE TOP indicates that processing is to continue at the
top of the processing loop. This starts the next repetition
of the processing loop.


ESCAPE BOTTOM indicates that processing is to continue with
the first statement following the processing loop. The loop
is terminated and loop-end processing (final BREAK and END
DATA) is executed for all loops being terminated.

Whereas if you specify the keyword IMMEDIATE, no loop-end
processing will be performed(i.e.,final BREAK and END DATA
is not executed for all loops being terminated).

In older version of ADABAS the limit used to be 32 files.
So now it will be eitehr the same or more.

If you wish to position the cursor to a specified field,
you can use the MARK option,
eg.
INPUT
MARK *#MAP.#ACTION
USING MAP 'IVCLNTM1'

and and to position to a
particular position within a specified field, you use the
MARK POSITION option.


DEFINE DATA LOCAL
1 #A (A10)
1 #B (N4)
1 #C (N4)
END-DEFINE
*
INPUT (AD=M) #A #B #C
IF #A = ’ ’
COMPUTE #B = #B + #C
RESET #C
REINPUT FULL ’Enter a value’ MARK POSITION 5 IN *#A
END-IF
END

Number of occurances in MU and PE can be found by c*field
name.

If Adabas file having MU field 'switch' and has 5 values.
then in module you can find it by C*switch. this will have
value 5.

Both used to read sequentila file.
Read work file 1:

1. is a processing loop strating like:
Read work file 1 file1
---
--
--
end- work.
Here ---> file 1 is file name here and 1 is arbitary file
number which is translated into dataset names CMwk01 in jcl.

read work file once:
1. Reads only one reacord is to be read.
2. there is no processing loop
eg. Read work file once

Read(1) file1 in physical sequence:
1. Used to raed adabas file.
2. here (1 ) represents the number of record to be read
its a processing loop eg

Read(1) file1 in physical sequence
--
---
---
end-read

read work file :
1. Used to read flate file.
2. Once option is used to read only one record
3. its not a processing loop

Hitogram retruns the one line output for each key value
from the inverted list. for histogram ADABAS does not have
access to data storage,therefore we can not do any update
add or delete using histogram.

An external subroutine can access the global data area used
by the invoking object(Program, Subprogram)
Moreover, parameters can be passed with the PERFORM
statement from the invoking object to the external
subroutine. These parameters must be defined either in the
DEFINE DATA PARAMETER statement of the subroutine, or in a
parameter data area used by the subroutine. Programs,
Subprograms and Subroutines Programming Guide
In addition, an external subroutine can have its local data
area, in which the fields that are to be used only within
the subroutine are defined.
However, an external subroutine cannot have its own global
data area.

I think directly this conversion is not possible as packed
decimal is used for numeric value fields only.
Since it is p(8) so the numeric value field size should be
15 or 16 as [8 can be either (n+1)/2 i.e. (15+1)/2 or ( n/2)
i.e. 16/2].
So we can say (n15 or 16) will be (P8).
Alternatively (A16 or 15)

In general the DDM is part of a single Adabas file and we
the programmers play around the views of DDMs.

It is possible that there can be multiple views of a same
file, but I never heard that there can be one DDM from
multiple files.

When developing a new program, make sure that you remove unwanted fields or views that are declared inside the DEFINE DATA section. Since when a program is compiled, it picks these fields also in the buffer memory during compilation and resources would be wasted and efficiency is affected.

Do not use unwanted READs inside a FIND statement.

Never use an UPDATE inside a physical READ.

Avoid using COMPUTE statements while performing straight forward addition, subtraction functions, rather use the appropriate ADD, SUB statements for it.

Its a special kind of discriptor,It is an extension of
Super descriptor and can have maximum of 20 fields.The
hyperdescriptor option can be used to generate descriptor
values based on a user-supplied algorithm.With
hyperdescriptors, “fuzzy” matching is possible; i.e.,
retrieving data based on similar rather than on exact
search criteria. Hyperdescriptors allow multiple virtual
indexes, meaning that several different search index
entries can be made for a single data field.

ADABASE the adaptable database, is a high-performance,
multithreaded, database management system for mainframe
platforms where database performance is a critical factor.
It is built on INVERTED LIST model.

Inverted List: it is used to resolve Adabas search commands
and read records in logical sequence, is built and
maintained for each field in an Adabas file that is
designated as a key field or “descriptor”.t is called
an “inverted” list because it is organized by descriptor
value rather than by ISN.

ADDRESS CONVERTOR:it contains the RABN's in ISN order. It
determines the physical location of a record. It is an
index that maps the logical identifier of a record (that
is, the ISN) to the relative Adabas block number (RABN) of
the Data Storage block where the record is stored.

DATA Storage:It stores the actual record in the order in
which it was entered

A control variable is used to dynamically set attribute and
colour definitions for a field or group of fields depending
upon a program condition. For example, Consider an order
processing screen that allows you to create new contracts,
modify existing contracts and look-up paid-up contracts.
The screen used for all these functions is the same.
However, when a paid-up contract is shown to the user, you
do not expect it to be displayed in a modifiable state. So,
you protect all the fields of the map and show it
like "read only". However, for modifying an existing, non-
paid-up map, you enable certain fields. So, control
variables can be used in scenarios like this to dynamically
set the attributes of the field.

steps are as below
1. file should be in sorted order
2. you can use either at break statement on the descriptor
and then do the validation or you can used desctiptor field
for comparison of secod record and first record, if the
descriptor values are same then escape top

yes we can find out the copy book length by using fileaid

1-6 sequence numbers.

7 (*) for comment (-) for continue (D) for debugging.

8-11 called as Area-A in this Area we can write
Divisions,Paragraphs,sections,Level numbers.

12-72 called as Area-B in this area we can write cobol
executable statements like select,accept,display.

73-80 is ignored area by compiler but we can see in source
Listing.

CALL statement can have max 128 parameter

An External Subroutine has got access to the Caller's GDA
where in the subprogram does not have.

The subprogram is like blackboxes as they are not aware of
the caller's environemnt. They take only the parameters and
process it and return the values. e.g. One natural
subprogram can be called through middle tiers like Entirex
and Vitria from a different environment(Lets say a dot net
or java developed web interface).However a similar
interface can not call a natural external subroutine.

As far as calling is concerned you use callnat for
subprogram and perform for external subroutine.

You use the following steps to check whether the input file
is empty

Step A. Read work file #WK-Number once #WK-Record
Step B. At End of File
Write "Input file is Empty"
End-Endfile

The first step will read the first record in the file and
the next step will see the End of File condition. If the
File is empty, the program will write that we have an Empty
input file to spool.

Escape Routine is generally used to interupt the processing
of Subprogram or Subroutine to return Control back to the
next statement from where this subprogram or routine was
called.

This statement will return an error if not placed within a
subprogram, subroutine or processing loop.

Parameters can be passed with the PERFORM statement from
the invoking object to the
external subroutine. These parameters must be defined
either in the DEFINE DATA PARAMETER
statement of the subroutine, or in a parameter data area
used by the subroutine.
An external subroutine can access the global data area used
by the invoking object.
In addition, an external subroutine can have its own local
data area, in which the fields that are to be used
only within the subroutine are defined.
However, an external subroutine cannot have its own global
data area.

Yes, it is possible. The below JCL can list the source of
the Natural program to a dataset and it can be very well
downloaded using option 6.

//STEP1 EXEC NATBATT
//SYSOUT DD SYSOUT=*
//CMPRINT DD DSN=USERID.MYNATPGM,
// DISP=(NEW,CATLG,DELETE),
// SPACE=(CYL,(1,1),RLSE),RECFM=FBA,LRECL=133
//SYSIN DD *
LOGON NATLIB
L MYNATPGM
FIN
/*
NATLIB = YOUR NATURAL LIBRARY
MYNATPGM = YOUR NATURAL PROGRAM

We use File aid for sequential files for the following
reason:

1. Copy from one file to another only selected amount of
records.
2. To browse or edit through the file using a copybook.
3. For impact analysis on a particular file.