This is Geetha.  I have 11 years of experience in IT Industry.  Mainly I spent my time in Mainframes and team management.  Here, I started sharing Mainframe Interview Questions with Answers and this is Part I.

Mainframe / General IT Interview Questions with Answers:

Q: Explain Paging Concept in memory.  
Whenever a particular data item is requested, the CPU hits primary memory or RAM first to see if the record corresponding to the data item is present in any page in primary memory. If not, it does paging and brings in the correspong page from secondary/auxiliary memory or hard disk to primary memory and then returns the data item to the user.

Q: What is Defragmentation and What is its advantage?
A: The process of combining the scattered allocated spaces for a file in a single or few contiguous areas rather than multiple areas is called defragmentation. Defragmentation reduces the number the seeks to retrieve the data.

Q: What is downtime and what might be the reason?
A: Downtime is the very brief period that the system is not available. It is generally done for maintenance activities for the mainframe. In the rare cases, it is due to system outage.

Q: What is SLA?
A: SLA is Service Level Agreement between the customer and the vendor. It is significant in support systems wherein the terms could be like response should be given within two hours that an abend has occurred or for online systems, the system should not be down during user daytime.

Q: What is a Configuration Management system, give examples?
A configuration management system is typically used in development environments to maintain versioning of the developmental code to avoid any overlay of code by different developers working on the same code. It helps maintain the integrity and consistency of the code across environments.
CHANGEMAN and ENDEVOR are examples of configuration management in mainframe.

TSO and other:

Q: What is the keyword to compare specific columns in SUPERCE compare?
A: CMPCOLM <start:end>

Q: How to search for a numeric string using find command?
A: f p’#’

Q: What is the line command to compress a dataset to avoid space abend
A: z

Q: How to save a dataset when you are in view mode?
A: give the command REPL .zf .zl and hit the enter key to save the changes
This replaces the currently open dataset with the new data from start to end line of dataset.

Q: What is the command to list all open screens in TSO?

COBOL Interview Questions with Answers:

Q: How to determine whether looping is occurring in a PERFORM statement?
A: Give display statements for each iteration

Q: What is the error corresponding to file status 23?
A: Record not found

Q:What is the reason for SOC7 abend?
A: Non-numeric data is moved to numeric field

Q: What is the reason for S806 abend?
A: No active load module found. Most common reason this could occur is due to spelling mistake of program name or giving different program name in the RUN JCL.

Q: What is the level of working storage variable used for specifying conditional names?
A: 88

Q: What is the purpose of SYSLIB ddname in COBOL compile JCL?
A: It is used to specify any copy library that may be used by the program

Q: What is the purpose of compile option DYNAM?
A: This is used to signify whether the compiler dynamically loads sub-programs when a call is made to them.