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Top 20 Mainframe Testing Interview Questions

Mainframe systems, which first came into existence in the 1950s, are considered legacy technology. With development and innovation in technology as a whole, they have become sophisticated and powerful, with the ability to handle extensive calculations and huge data processing.
Mainframe testing is the process of evaluating software, applications, and services on mainframe systems. With mainframe testing, the dependability, performance, and excellence of mainframe systems can be ensured through verification and validation.
When an individual is interviewing for a mainframe testing position, he/she has to have thorough knowledge of mainframe system as well as mainframe testing process.

Mainframe Testing Interview Questions

In this article, we present some common interview questions that can help you sail through the interview.

1. Where is the Mainframe technology/systems used?

A mainframe system is a powerful, large-scale computer system. It is especially designed for tasks related to high-volume data computing and complex calculations. Mainframes are designed such that they can handle massive data, support numerous simultaneous users, and offer other superior features. Mainframe systems are used in real-time applications such as banking and finance, business transactions etc.

2. What are the advantages of mainframe systems?

Some of the advantages of mainframe systems are:

3. What is Mainframe Testing?

Mainframe testing is the process of testing mainframe systems and other applications and services running on mainframes. Mainframe testing involves batch and online testing. It is performed to ensure that the software applications and services on mainframe system are verified and validated and that the system is ready to deploy.

4. What is the difference between mainframe and manual testing?

There is no difference between mainframe and manual testing as far as the process is concerned. However, the main difference is the technology used. The mainframe testing uses mainframe host systems or CICS screens. In manual testing, the web applications or desktop applications with GUI are used.

5. What can be tested under mainframe testing?

Mainframe testing has a huge scope. Successful mainframe testing indicates the mainframe system is ready to deploy. However, exactly what is tested depends on the project and its requirements. At a high level, files and databases are validated, and JCL runs under batch testing. Under online testing, the front end is tested.

6. Explain the attributes of Mainframe testing.

There are four attributes of mainframe testing:
  1. Batch Processing
    In batch processing, a task is divided into units called jobs. A batch consists of jobs executed sequentially.
  2. Multiprogramming
    In multiprogramming, more than one application runs simultaneously. But the CPU is used by only one program at a time.
  3. Virtual Storage
    A processor simulates the main storage larger than the actual storage. This is the virtual storage. Virtual storage is used to store and perform various tasks with memory.
  4. Time-sharing
    In mainframes, every user has access to the mainframe system through a terminal device on a time-sharing basis. Commands entered are processed immediately.

7. What are the different types of datasets in the mainframe, and how do they differ?

Mainframe systems primarily support three types of datasets.In sequential datasets, data is stored in linear format while the partitioned datasets allow for multiple members within a single dataset. VSAM provide advanced data management capabilities used for high-performance applications.

8. What is Customer Information Control System (CICS) in the Mainframe? What role does it play in mainframe systems?

Mainframes use transaction processing system called CICS. CICS manage and optimize real-time business applications and ensures high availability and reliability for critical transactions.  

9. What is JCL, and why is it essential in mainframe testing?

JCL stands for Job Control Language and is a language that controls jobs in mainframe systems. It gives instructions to the system for a batch process. JCL is a collection of instructions used to inform the operating system of the action to be taken.
JCL is a scripting language and is usually a large program.

10. What are the types of JCL statements?

JCL has three types of statements:

11. What is SPOOL?

SPOOL stands for Simultaneous Peripheral Operations Online. SPOOL is a mechanism wherein data is stored in a large storage medium to be retrieved a another time. It is kind of a buffering mechanism.

12. Explain SPUFI?

SPUFI is an abbreviation for SQL Processing Using File Input. Objects in the database are built using a menu-driven tool. SPUFI has a level of isolation, which is the degree to which the focusing group is insulated from the simultaneous execution of activation groups.

13. What is DRDA in mainframes?

Distributed Relational Database Architecture, or DRDA, is a set of rules that allows users to access distributed data, irrespective of whether they are stored physically. It is a connection protocol for RDBMS processing and contains rules for communication between a remote RDBMS and the application. DRDA is mainly used by IBM.

14. What is COBOL?

COBOL stands for Common Business Oriented Language. This object-oriented, procedural, and imperative language was developed in the 1950s by the US Department of Defence as a means of communication between different mainframes. Some of the features of COBOL are:

15. What is the purpose of the DB2 database in the Mainframe?

DB2 is relational database management system. In mainframes, DB2 is used to manage and retrieve large volumes of data. DB2 also supports high-performance, mission-critical application and ensure data integrity and availability.

16. What is the difference between batch testing and online testing?

Mainframe testing is of two types: Batch testing and Online testing. Batch testing is essentially a back-end testing and is responsible for running JCL, validating files, databases, etc.
Online testing deals mostly with front-end testing. In this, the GUI is tested by entering some values and verifying the response based on the system. Online testing is done for real-time systems.

17. How can you handle a situation where a batch job is running longer than expected?

One possible answer is to first check the system logs that record events in the system to identify possible bottlenecks like high CPU usage or I/O waits. Job settings can also be reviewed to ensure it has enough resources to complete the job. If required, code can be optimized or the job can be further broken into smaller units to improve performance.

18. Name different types of tablespaces in mainframes?

Mainframes use three types of tablespaces:

19. What is a GDG (Generation Data Group)?

GDG stands for Generation Data Group. It is a collection of historically related non-VSAM data sets arranged in chronological order. Each GDG set is historically related to other sets in the group. Some of the advantages of grouping related data sets (GDG) are:

20. What do you know about a Jobcard in JCL?

JOBCARD is the first statement in JCL. It identifies a job or unit of work (UoW) for the mainframe system to perform. Only one job is allowed to have one JOBCARD. A jobcard starts with ‘//’.

Conclusion

The questions and answers covered in this article should give required confidence to the candidate answering mainframe testing interview. We hope this will help the tester to crack the interview and land the dream job!