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

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. What do know about RACF in mainframes?

Ans: RACF is an acronym for resource access control facility. It is an Extreme Security Manager(ESM) for mainframe operating system. RACF stores all information about users groups and resources in profiles. A profile is a record of RACF information that has a record of RACF information which is defined by the security administrator. There are three profiles as follows.

1) User Profile:

An individual member identified by his unique id and verified using a password.

2) Group Profile

A group is a collection of RACF users who share common access requirement to protected resources or who have similar attributes within the system.

3) Resource Profile

Any information stored on a computer system such as datasets, Terminals, volumes etc. There are two types of Resouce Profiles.

  • Dataset Profiles.
  • General Resource Profiles.

. What is JCL in mainframe?

Ans: JCL in an acronym for Job Control Language. JCL is a scripting language used on IBM mainframe operating system for instructing the system for the batch job. It is a set of statements which is coded to tell the operating system about the task you would like to perform. This set of statements can also be quite large, but most jobs can be run using a very small subset.

JCL statements notify the OS on the following.

  • Where to find the required input?
  • How to process that input? 
  • What to do with the resulting output?

. How many types of JCL statements are there for a job?

Ans: There are three main types of JCL statements for all jobs:

  1. The first statement is to identify the unit of work that the operating system is to perform.
  2. The second statement is EXEC statements, depending on the number of job steps within the job.
  3. The third statement is DD statements to identify the input and output data sets.

. How is a type of file defined in the JCL that executes the COBOL program?

Ans: SORTWK01, SORTWK02, SORTWK03 … dd Use the names in the step. The number of sorted data hang on the size of the sorted data, but at least three is required.

. Express the distinction between JES2 and JES3?

Ans: 

  • In JES3, the distribution of informational indexes for the means happens prior to the activity is planned for execution. 
  • In JES2, this assignment happens prior to the execution of each progression.

. Define DB2 and its Databases?

Ans: 

  • DB2 is a part of data management product, including database servers, developed by IBM. DB2 supports the relational model. 
  • At present days, few products have extended their functionality to support object-relational features and non-relational structure like JSON and XML. 
  • A DB2 database is a collection of different type of data like Tables, Schemas, Bufferpools, Logs, Storage groups, and Tablespaces. 
  • These data substances work together to handle database operations efficiently.

. What are the rules for DB2 programming?

Ans: The rules that are necessary for a COBOL-DB2 program are as follows:

  • All the SQL statements must be delimited between EXEC SQL and END-EXEC.
  • The SQL statements must be written in Area B.
  • All the tables that are used in a program must be declared in the WorkingStorage Section. This is done by using the INCLUDE statement.
  • All SQL statements except INCLUDE and DECLARE TABLE must belong in the Procedure Division.

. Name and explain the type of locks?

Ans: There are three types of lock, namely:

  1. Shared: This type of lock permits two or more programs to read from the locked space but does not allow them to change it.
  2. Update: This lock is more lenient. It permits the program to read and change the locked space.
  3. Exclusive: This lock restricts all users from accessing the locked space.

. Define deadlock in DB2?

Ans: When an independent process gets contended for the same or reserved resource of one another, then it is called a deadlock. The SQL codes for deadlock are -911 and the -913.

. What parameters are used to control the free space in DB2?

Ans: Free space permits the addition of new rows. There are two parameters, which are used to control the free space in DB2, they are:

  • PCTFREE: It defines the free space percentage that will be present on each page.
  • FREEPAGE: It specifies the number of pages to be loaded before leaving a page empty.
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. What is CICS?

Ans: 

  • CICS is an acronym for Customer Information Control System. It was introduced by IBM in 1968. 
  • It provides an MVS environment to develop and execute an online application. At present days, CICS has become the most generally used server for Internet applications.
  • It is a transaction processing system which is also called as OLTP (Online Transaction Processing Software). 
  • It is a data communication system that supports a network that has hundreds of terminals.

. What are the CICS Transactions?

Ans: CICS transactions perform multiple operations in the CICS region such as defining CICS table entries, updating records, etc. 

Few important CICS transactions of IBM are as follows.

  • CESN (CICS Execute Sign On)
  • CEDA (CICS Execute Definition and Administration)
  • CEMT (CICS Execute Master Terminal)
  • CECI (CICS Execute Command Interpreter)
  • CEDF (CICS Execute Debug Facility)
  • CMAC (CICS Messages for Abend Codes)
  • CESF (CICS Execute Sign Off)
  • CEBR (CICS Execute Temporary storage Browse)

. What is the function of DBCTL?

Ans:  DBCTL is used for accessing the IMS files for CICS Transactions and it is address space. PSBs, DBDs, IMS files and ACBs are fixed into DBCTL for file access. When an IMS call is generated by a CICS program the processing gets transferred to DBCTL to be carried, and the result is sent as a reply.

. What are VSAM Commands?

Ans: VSAM commands are used to perform operations on the datasets of VSAM. These commands are used to manipulate the datasets as per the need.

Some of the most important and useful VSAM commands are

  • Alter: It is used to modify the file attributes of the VSAM
  • Repro: It loads the data in VSAM dataset and also to copy from one VSAM dataset to another
  • Listcat: It helps in fetching the catalog details of a VSAM datasets
  • Examine: It is used to verify the structural integrity of a key-sequenced data set cluster.
  • Verify: It is applied to crosscheck and verify to fix VSAM files which may not be closed in a proper way due to error.

. Which are the main components of a VSAM?

Ans: There are three main components of a VSAM-

  1. VSAM cluster.
  2. Control Area.
  3. Control Interval.

. Please tell me what is load balancing in Citrix?

Ans: 

  • Load balancing is a feature that distributes client requests across servers for optimum utilization of the resources.
  • In a real-time scenario, the services are provided to a large number of clients from a limited number of servers.
  • To reduce the load on servers, the system selects certain servers.
  • These servers implement certain criteria to forward incoming requests.
  • There are virtual servers that identify the server using the load balancing criteria.
  • When the client connects to the server, the virtual server terminates the connection and initiates a new connection with the selected server.

. Name a few load evaluators that are supported in Citrix?

Ans: Load evaluators that are supported in Citrix include:

  • Scheduling
  • User Application Load
  • Server Application Load
  • Page Fault
  • CPU Utilization
  • IP range
  • Context Switches
  • Page Swap etc

. Do you know how to implement policies to streamed applications in Citrix?

Ans:

  1. Open the application profile with Streaming Profiler.
  2. Move to Target and click on Edit -> Target Properties.
  3. Move to Rules Tab.
  4. Add an Ignore Registry rule that is similar to the description | CTX10352.
  5. The GPO’s of the domain will be applied.
  6. Customize GPO configuration.

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. What are simple, segmented and partitioned table spaces in DB2?

Ans:

Simple Tablespace:

  • Can contain one or more tables.
  • Rows from multiple tables can be interleaved on a page under the DBAs control and maintenance.

Segmented Tablespace:

  • Can contain one or more tables.
  • The tablespace is divided into segments of 4 to 64 pages in increments of 4 pages. Each segment is dedicated to a single table. A table can occupy multiple segments.

Partitioned Tablespace:

  • Can contain one table.
  • The tablespace is divided into parts and each part is put a separate VSAM dataset.

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Groovy is a subset of the java language and shares a good market in recent times. If any of the java programmers are looking out for a career change, here you go. We are going to design Groovy interview questions and answers under the guidance of the SEO team and Groovy experts. In this Groovy interview questions and answers post, you will be learning the very important questions which are asked by top companies. Kick start your Groovy professional career with the help of frequently asked Groovy interview questions and Answers. 

Most Frequently Asked Groovy Interview Questions

What do you know about JVM (java virtual machine)?

Ans : JVM stands for Java virtual machine and they are considered to be an important component of Groovy runs. So Groovy needs the JVM to perform many java-based tasks. 

What do you mean by Groovy?

Ans : Groovy is basically an object-oriented programming language and it has been a top choice for many programmers to write and execute their Java codes. The reason behind its popularity is its customization features to any extent. And also last but not the least, the best user interface services. So it is very easy to develop applications with the help of the Groovy user interface.

What are the true reasons behind Groovy popularity?

Ans : Here we would like to mention a few reasons behind its popularity among other java programming languages.

  • Groovy can be used for scripting like log configuration.
  • It is not a fully object-oriented programming language.
  • It mainly uses Java libraries and multiple inheritance.
  • It offers native support for various markup languages like HTML (hypertext markup language) and XML (extended markup language). 
  • It has a public modifier.
  • It supports tools like Gradle and Spack 
  • It also consists of tools that support other programs to run. For example Grails and Java

Could you please mention the benefits of using Groovy?

Ans : Below are the primary advantages of using Groovy;

  • Compile and execute with all the java libraries that include a part of the COAT JAVA installation.
  • It offers very light syntax while writing a program
  • Offers several examples in the software center.
  • Less work is required during the time of processing HIPO files as input.

What are the limitations of the Groovy language?

Ans : Here are the few disadvantages of using the Groovy language:

  • Having to use GROOT means not having all the plotting and fitting power associated with ROOT as GROOT is a smaller subset of the ROOTs plotting and fitting.
  • Need to know JAVA which is less common for psychic-based analysis

Explain the concept of thin documentation in Groovy?

Ans : This is a very common issue in almost all object-oriented languages. The real problem behind this inaccuracy is that Groovy doesn’t provide detailed documentation on the projects or code. Therefore you will get limited documentation with no information regarding programming codes or run-time errors

How can you run the script in Groovy?

Ans : Running script is a nit a big deal for many programmers. All the plain scripts are very easy to run on a Groovy, and one good thing is that there is no need for programmers to declare any class or methods which consume extra time. At the beginning of any script, that enables the programmers to use import values. This process is very similar to implementing them in a class. In case you want to declare a function outside the class, you can make use of the command “def

Name a few infrastructures that can be used along with Groovy?

Ans :The following are the name of a few infrastructures that can be used along with Groovy;

  • App servers
  • Servlet (java servlet) containers
  • Databases having JDBC drivers
  • All other java based programs. 

Do you really think that Groovy is a simple language than others if so give reasons?

Ans : Yes, most of the developers agree that Groovy is a simple language to use and code. The reasons are as follows;

  • Users can enjoy a simple declaration of all the arrays, maps as well as ranges. 
  • This makes programmers proceed with multiple tasks and they can expect effective outcomes s

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. Is it possible for you to integrate with other applications that are not based on Java?

Ans : Yes, this is possible. However, only one problem with Groovy integration is that it offers limited features that cannot be used to handle complex programming.

. What are the basic requirements for Groovy?

Ans : The primary requirements that are needed for Groovy are as follows:

  • The Java 1.4 version.
  • The Groovy. Jar 
  • The ASM libraries

. What do you mean by Groovy applications?

Ans : Apache Groovy is one of the powerful approaches used in the different modules. The very first thing that comes to mind is adjoining the different modules of java. It doesn’t matter the size but they can be easily combined with the different Java modules. In addition to this, all the existing java applications can be extended through Groovy very simply. This process also makes it easier to develop java-based applications without any error. There are several other applications available, but they are quite common.

. What are the features Groovy JDK equipped with?

Ans : Below are the common features that Groovy JDK (java development kit) is equipped with;

  • Using Groovy is simple as it does not require any complex things to implement the applications.
  • It doesn’t matter which operating system you are using and what are the components of the server, it is easily made up to perform various tasks as per the requirements.
  • In addition to this, there are other features available to run the application smoothly based on Java. 

. Compare the old version of the Groovy with the new version?

Ans : When it comes to the new version, there are a lot of advanced features that are quite simple to use when compared to the older version. With the help of the new version, it is also possible to stream arrays and objects of object-oriented methods used in the older version. In addition to this, a lot of run time errors have been eliminated at various stages and commands also have been improved for smooth operations.

. Suppose you are running something on Groovy, is it possible for you to add any data or for the classpath?

Ans : The answer would be yes it is possible. To perform this task, a $classpath variable can be considered. Some programmers also build the $HOME- -> a.groovy – ->lib directory for this. It can simply be defined in the $HOME and users can keep up the pace at every stage

. What do you know about listeners and closures in Groovy?

Ans : Groovy does not support all types of asynchronous inner classes. Users need to be more conscious about the class that they are going to use while defining the functions. In the Groovy also, you will get to see two different types of classes, firstly listeners. In the listeners, the closures can be considered as an adapter for the listener that offers no limit for the inner class implementations. Whereas the closures are nothing but a process of determining the actions that are extremely easy to use.

. Is there any limit on appending the jars that are available in the groovy?

Ans : No there is no such limit, programmers can make them available in any number whenever they need them.

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. What is the importance of using ExpendoMeta class in Groovy?

Ans : Expendometa class is a powerful option available in Groovy. With the help of this class, the programmers can able to add and consider properties, constructors, methods, and operations to perform various tasks. By default, ExpendoMeta cannot be inherited and users need to call it whenever they required it. 

The following command is used to declare ExpendoMeta class;

ExpandoMetaClass.enabledglobally()”.

. What factors do you need to take care of while declaring Groovy strings?

Ans : Below are the important factors you need to take care of them;

  • All the expressions which are used in Groovy must be declared using the ${}.
  • The next step is, it should be joined by double-quotes. 
  • However, if the strings are regular, you can use a single quote.
  • The Square bracket [] in the Groovy can be applied in a very general manner.
  • Also, users need to remember one thing that is Groovy string is also known as Gstring.

. In Groovy, from the database how can you derive a single class?

Ans : This can be done with the help of the following command;

Println “Row; ColumnA = $”.

There is another option that is also available to do so manually but it is a complex one and there are certain sets of modifications required which will never be performed by programmers

. What is querying in Groovy? Why there is a need for it?

Ans : Querying in Groovy is basically an approach that is used to detect whether the set of commands is compatible with the required operations or not. Also, it can be considered when users need to verify or cross-examine something. The Groovy is an approach that has support for the various queries and the same thing can be handled. The primary task of Querying in Groovy is to ensure error-free outcomes under every situation.

. What does the AST stand for?

Ans : AST in Groovy stands for Abstract syntax trees.

. Explain the AST builder in Groovy?

Ans : In DSL (data syntax language), the codes, as well as strings, are extremely useful factors. This type of task is reliable and there is nothing much that the users need to do. While building AST, sometimes this process might take several hours that depend on the exact number of tasks that are under a tree structure and how they are to be handled.

. Can we include one Groovy script into another Groovy?

Ans : Yes, it is possible. To perform this operation, you need to follow the below codes.

Evaluate(new file (“../tools/Tools.groovy”))

Always remember one thing, place the code on the top of the script for copying the contents.

. What do you mean by Groovysh?

Ans : Many a time while developing codes programmers have to go through a complex when it comes to evaluating classes, expressions, as well as running the experiments. Groovysh is considered to be a powerful command-line application that makes sure of easy access to the same. Groovysh is used at many stages and the good thing is programmers can call it directly. 

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. How could you retrieve a single value from a database using the Groovy?

Ans : The following are the command is used to retrieve a single value from a database using the Groovy;

row = sql.firstRow ('select columnA, column from tableName')

println "Row: columnA = $ {row.columnA} and column = ${row.columnB}"

wing are the command is used to retrieve a single value from a database using the Groovy;

. Explain how you can query in Groovy with code example?

Ans : Let’s have a look into a simple example where we can query the database in Groovy:

import groovy.sql.sql

sql = Sql.newInstance ('jdbc: jtds: sqlserver://serverName/dbName-Class;domain=domainName','username','password','net.sourceforge.jtds.jdbc.driver')

sql.eachRow ('select * from tableName') {print "$it.id--${it.firstName} –"  }

. Explain GroovyDoc comment?

Ans : Like other multiline comments, Groovydoc comments are multiline but it starts with a /** and ends with */. These comments are related to

  • Type definitions (classes, interfaces, enums, and annotations).
  • Fields and properties definition.
  • Methods definitions.

. Explain the bitwise operators in Groovy?

Ans : Bitwise operators in Groovy can be implemented on a BYTE or an INT a return and INT. There are four types of bitwise operators in Groovy;

  • &: bitwise “and”
  • I : bitwise “or”
  • A : bitwise “xor”
  • ~ : bitwise negation

. When “propertymissing(string) “ method is called?

Ans : The propertymissing(string) method is called when no getter method for a given property can be detected by the Groovy runtime.

nal thoughts:

As per the latest reports, an average salary for any Groovy developer earns Rs. 8, 00, 000, and the salary will increase for an experienced Groovy developer. Groovy is the popular choice of Java program due to its less complexity and coding. In this post, we have listed very important Groovy interview questions with Answres under the supervision of Groovy experts. The companies like PWC, IBM, TCS, Amazon, Facebook, and Instagram are showing keen interest to hire Groovy developers 

About Author

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As a Senior Writer for HKR Trainings, Sai Manikanth has a great understanding of today’s data-driven environment, which includes key aspects such as Business Intelligence and data management. He manages the task of creating great content in the areas of Digital Marketing, Content Management, Project Management & Methodologies, Product Lifecycle Management Tools. Connect with him on LinkedIn and Twitter.

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