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Mainframe Interview Questions and answers


Wishing to crack the interview and create an impactful impression, one must answer the questions up to mark and tactfully. Testing Interview Questions is not easy; one needs to apply their knowledge correctly and answer precisely. Mainframe interview questions are significant; many opportunities and jobs are there in this field. To stand out among all the candidates is essential. An idea regarding the Mainframe interview questions which can be asked in a Mainframe interview helps one prepare accordingly and boosts their confidence. 

More about Mainframe 

Demand for Mainframe Developers is increasing day by day. Mainframe Developers can perform various activities and tasks related to Software like coding applications, designing, installing a software system, developing applications, and creating the ideal system.  The mainframe still carries out large-scale transactions and manages information. The scope is very high in this sector, and so are the opportunities. Getting a job as a Mainframe Developer can be good for one’s career. 

Mainframe interview questions

To crack the interview, the candidate must have deep knowledge about mainframe Languages, tools and databases. The Panel can ask such Mainframe interview questions. They are divided into primary, advanced, related to database, related to languages, etc. 

Basic mainframe interview Questions

Q.1) What is the File-Aid tool?

Ans. An application or a tool that helps in the processing of files online is called the File-Aid tool.

This term is often confused with the term File-Aid utility. One must know the difference and answer accordingly. 

Q.2) what can one increment use arithmetic Operations? [Frequently asked mainframe interview questions]

Ans. One can increment Subscript using Arithmetic Operations easily. One can even decrement it in the same manner. 

Q.3) Explain HDAM Database?

Ans. HDAM database helps to get quick access to root using a randomizer. Record keys place the record to the desired position as HDAM doesn’t have a separate index file to store the information. 

Q.4) What are Synchronic Peripheral Operations online?

Ans. Synchronic Peripheral Operations online are often referred to as spooling. Spooling provides economical use of devices by taking the benefit of buffering. 

Q.5) What is the full form of JCL? [Frequently asked mainframe interview questions]

Ans. JCL stands for Job Control Language. It supplies essential information which is required in execution work. JCL also checks and controls each job. 

Q.6) Tell us about attributes of Mainframe Computing?

Ans. Square Measure, Virtual Storage, Multiprogramming, Batch-processing, Time-sharing, and Spooling are some of the attributes of Mainframe Computing. 

Q.7)  Who is the pioneer of Mainframe Computing?

Ans. IBM is the pioneer of Mainframe Computing. 

Q.8) Name a few Software Square measures?

Ans. COBOL, JCL, CICS, DB2, etc., are some of the Software Square Measures. 

Q.9) Can one call Catalog to Instream? [Frequently asked mainframe interview questions]

Ans. No, it is not possible to call Catalog to Instream. However, Instream can be called to Catalog. 

Q.10) What are the two prominent cases regarding Label Record?

Ans. Label records can be standard or omitted. It is shown in the file description of the Data Division. If the Label Record is standard, it denotes the usage of disk files, but if the record is omitted, it indicates tape files, which don’t have any begin and end blocks. 

Q.11) State Identification of a word in the Computer Memory? [Frequently asked mainframe interview questions]

Ans. Word length can be used to identify the word in the Computer memory. 

Q.12) which level is more effective or efficient?

Ans. Level 01 is the most effective or efficient level. 

Q.13) what can be done to a record in an ESDS file?

Ans. The record in an ESDS File can be rewritten, but for this, the length of the record must be the same. Therefore, deleting the record from this file is not possible. 

Q.14) Describe Dynamic Call?

Ans. The dynamic call has in-built storage in an identifier. It has several different modules for each program, divided under the main program and subroutine. Routine under Dynamic Call is stored forever in the default state. 

Q.15) Name the types of evaluation statements?

Ans. Trues and variable-name are the two types of evaluation statements. Evaluate Statement ensures a different way for IF Statements and chooses from a processing actions list when control is applied on application from evaluating to the Statement. 

Advanced mainframe testing interview   

Apart from the basic questions, the interviewer can use advanced mainframe interview questions related to processes, definitions, and usage of codes to test the candidate’s depth of knowledge and understanding. Below are examples of such questions. Answers to these mainframe interview questions are mere guidance; the candidate can add more information or answer them in their own words. 

Q.16) When is a Bit on? [Frequently asked mainframe interview questions]

Ans. The bit is on when it is negative. In contrast, it is off when positive. In a computer field, a sign is stored in Bits. 

Q.17) Elaborate XCTL?

Ans. XCTL is used to take the operations further of a new transaction. Then, it transfers the control to other applications. Transaction Identity remains equal at the start and after XCTL. 

Q.18) what do you mean by Mainframe Testing?

Ans. These mainframe interview questions are asked often and the checking of Computer codes and applications used in the system is known as Mainframe Testing. It supports the development of applications, price and quality. Therefore, it is crucial and has a lot of importance. 

Q.19) Mention a few producers of Mainframes?

Ans. Because of the prohibitive cost of development and deployment, only a handful of manufactures make and develop mainframes. Primary Producers of mainframe equipment and Software include IBM, Hewlett-Packard, Unisys, Fujitsu, Hitachi, and NEC. These manufacturers supply mainframe equipment to clients in both the public and private sectors. 

Q.20) What do you think about Mainframe systems and memory? [Frequently asked mainframe interview questions]

Ans. Mainframes can process thousands of million instructions per second. Mainframes can also have sizable primary storage capacities. Their main memory capacity can range from hundreds of gigabytes to many terabytes of primary storage. 

Q.21) State the connection between Mainframe and Python?

Ans. Python is one of the technologies that support interfacing with Mainframe. Another such technology is Ulpath. Various other technologies are also used as suitable for the client or developer.

Q.22) which is a VMS message? 

Ans. NOT 2 is a VMS message. It shows entries that are the same which exist in the Catalog. It helps us find the error. Rectification can be done quickly because of NOTCAT 2, either by cataloguing or deleting the entry. 

Q.23) what is the initial value order of SearchSearch All? [Frequently asked mainframe interview questions]

Ans. The initial value order of SearchSearch All is ascending. Sorting order can be ascending or descending of Search All. The table must be loaded in the order stated. To apply for the descending order, one must switch by providing descending key Clause. 

Q.24) Tell something about Using-In-line Perform?

Ans. Using-In-Line is a code used in several places and locations in the program, and the code should be used in different para. The adequate time is when the performance body is not in use. 

Q.25) Define Soc-7 error and how to rectify it?

Ans. Soc-7 error is mainly related to the un-initialization of a numeric item. Rectification can be done by invoking OS Services or subroutines using the assembly language. The dumps give us information about the place where the occurrence of amending took place. The line number and the verb of the offset code must be obtained by verifying the output XREF listing of Compilation. After these steps, the bug is found; then, the datasets should be defined to capture the run time dumps. If this method doesn’t work, one can see the error with the help of judgement and display. Use of debugging systems and utilities can also be done. 

Q.26) Throw some light on the security system in Mainframe? [Frequently asked mainframe interview questions]

Ans. The security system in Mainframe is powerful and cannot be hacked. There are very few entry points to access the raw data. Mainframe provides end-to-end encryption. The Data is only decrypted when the transaction is processed. Mainframes are mainly used for computation-intensive applications, such as analyzing seismic data from oil field explorations or simulating flight conditions in designing aircraft. 

Q.27) State some advantages of using Mainframes in today’s world? [Frequently asked mainframe interview questions]

Ans. Advantages of using Mainframe in today’s world are as follows:

Scalability The IBM’s Z System processor, can move a lot of Data, instructions along with supporting parallel processing. For example, a batch job that copies billions of records from one file to another file structure can take minutes instead of hours.

Security There are three external security manager software products that protect the Open-World computing platform’s data, programs, transactions, and components.

Reliability Multi-processing of hundreds of TSO users, system tasks, online services, and batch jobs will not crash a processor: a mainframe LPAR image is designed to handle heavy loads. As a result, the processor won’t crack from overuse or over-heating. 

Virtual Computing Virtualization has been supported in the mainframe world for more than a decade. Red Hat, Linux, SuSE and other Linux distros requiring a physical machine can run virtual machines on a Z processor. 

Q.28) Name some common users of mainframes? [Frequently asked mainframe interview questions]

Ans. Some Common users of Mainframe are IT Departments, Banks, Insurance companies, Departmental Stores, etc. 

Q.29) what is the size of a word in the Mainframe system? [Frequently asked mainframe interview questions]

Ans. The size of a word in the Mainframe system is four bytes. So each word should begin from an address which can be divided by four. COMP SYNC helps align an item to the boundaries; it gets synchronized right and left. 

Q.30) what are Ssrange and Nossrange?

Ans. Ssrange and Nossrange are the compiler options for verification of the out of range state for the Subscript. Nossrange is the default option and ensures no flagging of runtime errors. Runtime errors occur when the Subscript or index is exceeding the acceptable range. 

These are some of the Mainframe interview questions related to various concepts and processes. One must have detailed knowledge about the terms related to the Mainframe Testing interview and its components. Below are some more questions often asked in an interview regarding the databases and languages applicable or used in Mainframe System.  The answers can be amended accordingly by the candidate. These questions and answers are for reference and give an idea about the nature of questions asked in a Mainframe testing interview. 

Db2 Interview Questions 

Q.31) Which Clause is referred to select a row in DB2?

Ans. WHERE Clause is referred to select a row in DB2.

Q.32) What is used to combine the results of different SELECT Statements?

Ans. UNION and UNION ALL are used for the said purpose. UNION eliminates all duplicates, and on the other hand, UNION ALL retains all the copies. The command is to be specified only once to delete the duplicates.

Q.33) Give some information about the LIKE Statement?

Ans. LIKE Statement is used to carry out partial SearchSearch, partial string matches. When one has to search for something using a specific attribute LIKE Statement can be used. 

Q.34) Get a list of employees who are not given any project? State the steps

Ans. SELECT EMPNO then FROM EMP; WHERE PROJECT IS NULL. The list of employees who are not given any work will appear.

Q.35) Declare Cursor Statement 

Ans. Declare Cursor Statement is used in working storage or the division of a procedure. It is executable. 

About Mainframe Programming languages and databases

COBOL related testing interview questions

Q.36) State the divisions of a COBOL program?

Ans. Identification Division, Environment Division, Data Division, and Procedure Division are the different divisions of a COBOL Program. 

Q.37) Specify the Data Types in COBOL?

Ans. There are three types of Data Types in COBOL, namely Alpha-numeric, Alphabetic, and Numeric.

Q.38)  Give an example of any three levels and their usage?

Ans. Level 66 is used for RENAME 

Level 77 is used for no subdivision of items.

Level 88 is used for condition names. 

(In Mainframe Interview questions, questions related to levels are asked often)

Q.39) What is the performance of a SECTION?

Ans. Performing a SECTION causes the performance of all the paragraphs included in a section. Performing PARAGRAPHS can be used for the performance of a selected part. 

Q.40) Can a Complex condition be given on a WHEN Clause?

Ans. Yes, the complex condition can be given on a WHEN Clause. 

JCL related mainframe interview questions and answers

Q.41) RECFM Parameter

Ans. RECFM Parameter is used to record the format of an output dataset. 

Q.42) what begins an in-stream dataset in JCL?

Ans. DD* Statement begins an in-stream dataset in JCL. 

Q.43) Elaborate JOB Statement in JCL?

Ans. JOB Statement in JCL plays an important role. It assigns a name to the job and also marks the job’s beginning. 

Q.44) SYSOUT Parameter is used for what?

Ans. SYSOUT Parameter is used to set the disposition of sysout databases of an entire job stream. 

Q.45) how can one start a job which has been stopped?

Ans. RESET Parameter can be used to start a job that had been stopped. 

About CICS mainframe Interview Questions 

Q.46) Mention Working Storage Fields?

Ans. Three Working Storage Fields are used for every field given in a map: length, attribute, and input/output fields. 

Q.47) where does one receive the attribute byte in the symbolic map?

Ans. The attribute byte can be received in a symbolic map on EOF. 

Q.48) what do you mean by BMS length of the field = 0?

Ans. This means data was not entered in the field. 

Q.49) what will happen if you use the ASIS option on RECEIVE?

Ans. If one uses the ASIS option on RECEIVE, the characters entered by the user will not be folded to uppercase. 

Q.50) CICS Program running needs which tables?

Ans. To run a CICS program; PPT, PCT, and RCT tables are needed. DCT and FCT can also be handy if required.  

Basic Tips

Mainframe Interview Questions mentioned above are for reference and related to the field, but other questions related to qualifications, personal information, and interests can be asked by an interviewee to gain information about the candidates and study their personality. One must prepare accordingly and answer truthfully.

  • Collect information about the job post, nature of work, and the company. 
  • Arrange all the documents and certificates properly.
  • Speak politely and clearly.
  • Pay attention to body language and look.
  •  Be disciplined and well-organized.
  • Don’t get stressed; answer the questions confidently and tactfully.
  • Answer only what is asked or explain the term asked. 
  • Don’t ask any personal questions to the Panel.
  • Listen to the interviewer carefully and then speak.
  • Keep your mobile phone on silent mode or switch it off. 


Above mentioned questions, DB2 interview questions and tips are for guidance and to boost one’s confidence. Knowing the type of questions that can be asked in an interview helps the candidates prepare themselves and gives them some vision. Many companies and the jobs offered conduct mainframe Interviews are also beneficial for the candidate’s career. The interview helps to know the person, their knowledge, goals, behaviour, and the candidates’ overall attitude. Cracking an interview is essential to set a mark and give a good start to the career. 

More Resources : Basic Embedded Systems Interview Questions | Full-Stack Developer Interview Questions for freshers | Java Technical Architect Interview questions | HTML and CSS Interview Questions with Answers

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