Top 30 Mainframes Interview Questions and Answers [Updated]

The mainframe is a large and multi-user computer system that performs critical applications, bulk data processing, consumer statistics, enterprise resource planning and transactional processing.

In this article, you can go through the set of Mainframes interview questions most frequently asked in the interview panel. This will help you crack the interview as the topmost industry experts curate these at HKR training.

Let us have a quick review of the Mainframes interview questions.

Most Frequently asked Mainframes Interview questions

Can you name a few software running under the mainframe?

Ans: IBM is the pioneer in the mainframe computing field. Few of mainframe software are COBOL, Enterprise COBOL, JCL, VSAM, CICS, DB2, etc. Other players in the market are Unisys (Clear path), Hitachi (zSeries), HP (NonStop) and Fujitsu(BS2000/ ICL VME) amongst many others.

What is DRDA?

Ans: DRDA is an acronym for Distributed Relational Database Architecture. DRDA is a connection protocol for relational database processing which IBM and vendor databases use. It consists of rules for communication between a remote relational DBMS and the application.

What guidelines should be followed to write a structured COBOL program?

Ans: Following guidelines to be following while writing a COBOL program:

Use ‘EVALUATE’ statement for constructing cases.
Use scope terminators for nesting.
Use in-line Perform statement for writing ‘do’ constructions.
Use Test Before and Test After in the Perform statement while writing Do-While statements.

What are some uses of the Evaluate statement? Explore the syntax of the evaluate statement?

Ans: Some general uses of Evaluate statement are as follows.

Evaluate supports multi-selection control during the program execution.
Evaluate validate multiple conditions in a single slot.
Evaluate statement in COBOL is similar to Case or Switch statements of other languages.
Evaluate is an assessment is a case statement and can be used to replace local IFS.

Syntax:

EVALUATE {Expression1}

WHEN Cond-1

Statement block-1

WHEN Cond-2

Statement block-2

WHEN Cond-n

Statement block-n

WHEN other

Statement block- other

END-EVALUATE.

How TEST BEFORE/AFTER works with PERFORM UNTIL explanation in COBOL?

Ans:

With TEST AFTER, Perform articulations are handled after that condition is checked.
With TEST BEFORE, Condition is checked first and then in light of the outcome Perform explanations are prepared.

What is the utilization of Linkage area in COBOL?

Ans: Linkage area is utilized as a part of COBOL if the program needs to speak with JCL by means of PARM parameter or program needs to speak with another program.

State the difference between GOBACK, STOP RUN and EXIT PROGRAM in COBOL?

Ans: The fundamental differences between GOBACK, STOP RUN, and EXIT PROGRAM in COBOL are:

GOBACK: It returns control to the calling program.
STOP RUN: It stops the present work unit and returns control to OS.
EXIT PROGRAM: It is utilized to leave a program that has been called by another program.

Explain Host Variables?

Ans:

Host variables are data substances defined within a COBOL program. They are used to forward values to and receive values from a database.
It can be determined under the File Section, Working-Storage Section, and Local-Storage Section or Linkage Section of a COBOL program.
It can have any level number up to 48. Level 49 is reserved for VARCHAR data items.
The data item name should begin with a colon (:) when a host variable name is used within an embedded SQL statement.
It enables the Compiler to differentiate between host variables and tables or columns with the same name.

Host variables can be used in one of the given two ways.

Input host variables:

These are used to specify data that will be conveyed from the COBOL program to the database.

Output host variables:

These are used to hold data that is returned to the COBOL program from the database.

How to declare Host variables?

Ans: The following syntax is used to declare host variables and includes tables in the Working-Storage section:

DATA DIVISION.
WORKING-STORAGE SECTION.
EXEC SQL
INCLUDE table-name
END-EXEC.
EXEC SQL BEGIN DECLARE SECTION
END-EXEC.

. What are the file handling steps involved in COBOL programming?

Ans: A data file is a collection of relevant records and a record is a collection of relevant fields. The file handling in COBOL program involves five steps.

Allocation: The files used in the program should be declared in the FILE-CONTROL paragraph of environment division. The mapping with JCL DDNAME is done here. Through this statement, the file is allocated to your program.
Definition: The layout of the file and its attributes are defined in the FILE SECTION of DATA DIVISION.
Open: Dataset is connected to your program using an OPEN statement. The mode of OPEN decides the operation allowed and the initial pointer in the dataset.
Example: The EXTEND mode allows only to write access and the pointer is kept on the end of the file to append.
Process: It processes the file as per requirement, using the I-O statements provided by COBOL such as READ, WRITE, REWRITE and DELETE.
Close: After the processing, close the file to disconnect it from the program.

. When the JOB statement is used?

Ans: JOB statement provides the job identity to an Operating System, in the spool and the scheduler. It is the first control statement in a JCL. The available parameters in the JOB statement help the OS in allocating the right scheduler. It is also useful for analyzing the required CPU time and issuing notifications to the user.

Syntax:

The basic syntax of a JCL JOB statement is below.

//Job-name JOB Positional-param, Keyword-param