If you are here looking for help to prepare for your next Mainframe interview, you are at the right place. Below are the top 20 Mainframe interview questions that are most commonly asked in Mainframe interview.
DRDA stands for Distributed Relational Database Architecture. It works as a connection protocol for local database processing. Database vendors like IBM use it. This architecture contains a set of rules that helps communicate between any application and database relation.
While working with a relational database system, the clause “WHERE” isolates an element or a row.
You can use the LIKE parameter and the CREATE statement to create the LIKE table. These tables are needed during the testing phase of the production environment.
The catalog columns are filled with default values and the end result during environment testing may not produce accurate results. Runstats is used to clear the default values of these columns.
If a COBOL program needs to speak with a JCL or another program through the PARM parameter, Linkage Area is used.
COPYBOOK stores the format of any record and uses the same design for another program. We can use the same COPYBOOK for a number of documents using the REPLACING choice if the format is the same.
INCLUDE and COPY are different in the way they work. They are used for extension of design in a program. The main difference is that INCLUDE is used for expanding at a pre-compiler time whereas COPY is used for expanding at a compiler time.
Foreign keys are attributes of a particular table that have matching entries to the primary key in another table. Foreign keys are used to build a relation between any two tables.
Self-referencing constraint is used to restrict the changes that can be made to the primary key through a foreign key. To implement this, the foreign key must define the DELETE CASCADE rule.
When two separate processes are fighting for the same resources, or the resource reserved for each other, the situation is called a deadlock. SQL code for a deadlock are -911 and -913.
In Type 2 index, the data pages get locked but index pages are not locked. In Type 1 index, the index pages are locked. Type 2 index is quicker than Type 1 index.
HIDAM has its separate index file based on the root segment. This file stores information about the pointer that denotes the position of data. Whereas, HDAM does not have a separate index file. The key field of each record is accessed through a randomizer that positions the record in the correct place in the database.
Referential integrity rule states that consistency needs to be maintained between primary and foreign keys. In other words, each foreign key needs to have a primary key.
Multiple indexes consist of 2 indexes, one for each table column. The composite index is just one index that consists of joint values of 2 columns of the table.
GOBACK gives control back to the calling program. STOPRUN stops current work execution to return control to the operating system. EXIT PROGRAM is used to quit a program and allow another program to pursue.
Denormalizing reduces the necessity of executing various relational joins. It also reduces the requirement of foreign keys.
Database Descriptor or DBD provides restricted access to the database when an object gets created, altered or dropped.
Tables whose relation is established through a foreign key are called delete-connected tables. Whenever a primary key is deleted, the foreign key in the corresponding table is also impacted.
Shared Lock- This type of lock allows more than one program to read from locked part but not change it.
Update Lock- This lock allows the program to both read and change the data in the locked area.
Exclusive Lock- This Lock is restricted and does not allow any program to even access the locked space.
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What are the different types of locks and how are they distinct from one another?
One of the most important functions of a mainframe is controlling the ability of computers to access files stored on the mainframe. Locks are used to set access capabilities on a file, and the different styles change how the users are able to interact with and manipulate the files. Your answer must demonstrate the key differences between the types to show you understand when each is most likely to be beneficial.
Example: “There are three different locks that can be applied to data space, with each changing the way users are able to access the data stored in the locked section. With an exclusive lock, all access to the locked space is restricted from all users, providing full protection to the data in the locked space.
With an update lock, the program accessing the locked space retains the ability to read or even change the information in the locked space. Finally, with a shared lock, multiple users are able to access the locked information, however, they are unable to alter it, which helps to avoid conflicts from concurrent changes.”
How do TEST BEFORE and TEST AFTER perform differently when used with PERFORM UNTIL?
The most important questions an interviewer is likely to ask you pertain to the technical aspects of the job you are applying for. Its important to show your knowledge in these questions and demonstrate your comfort working with mainframes. This question requires the ability to understand why behaviors occur as they do and not simply an understanding of what differences exist. Be sure to include why the behavior differs from one option to the other.
Example: “The difference between a TEST BEFORE and TEST AFTER primarily comes down to whether the action will be guaranteed to be performed at least once or not. Since TEST BEFORE checks the condition before each iteration, if the initial state does not satisfy the test then it will never be executed. With TEST AFTER, the check is made at the end of each iteration. This means that if the initial check does not meet the requirements, it will still be iterated one time before the test is made and iteration is exited.”
What is the difference between composite and multiple indexes?
Often when working with mainframes, there are multiple terms that have similar meanings and functions but are not the same. Its common for a hiring professional to ask you to differentiate between similar terms and their functions.
Example: “While they may seem similar at first blush, there is a key distinction between a composite index and a multiple index. In a multiple index, two different indexes are used, with each receiving its own column. In a composite index, only one column is devoted to storing the index information, with the two indexes assigned to each row combined into one single column in the table.”
Top 5 Frequently Asked Mainframe Interview Questions
DRDA means Distributed Relational Database Architecture. It is a connection protocol that is used for local database processing. IBM and other vendor databases use it. It contains a set of rules which is used for communication between an application and a DBMS distant relation.
The clustered index is a unique type of index. This rearranges the order or manner in which the data or information of the table are stored. Also, the rows due to this type of index are stored on the disk, physically as per the index. Hence, there exists one single type of clustered index for one table. And the data pages are stored in the leaf nodes of this clustered index.
The difference between Version Control and debugging tools can be stated as Version control, also known as source control, is the practice of tracking and managing changes to software code. Whereas Debugging tool is a computer program that is used to test and debug other programs. A lot of public domain software like gdb and dbx are available for debugging.
An EXEC LINK is similar to a call; it invokes a separate CICS program and ends with a RETURN to the invoking program whereas an EXEC XCTL transfers control to another CICS program and does not get control back. And COBOL II allows for static calls which are more efficient than the LINK instruction which establishes a new run-unit.
First of all, SPUFI stands for SQL Processore Using File Input. This is a type of database provision, developed by the well-known IBM for the system that they provide, known as DB2. With the help of this users get to put the SQL commands directly into the TSO environment. This way they do not have to embed the commands of SQL into the program.
Static SQL is also known as Embedded SQL is a database access procedure that is predetermined in the statement such that these SQL statements in an application do not change at runtime and can be hard-coded into the application. Whereas Dynamic SQL is SQL statements that are constructed at runtime and are less efficient such that the application may allow users to enter their own queries.
Define WHERE and its usage?
The clause “WHERE” isolates a row or an element during the usage of a related system.
FAQ
What are interview questions about mainframe?
- What are the advantages of Mainframe Computers? …
- Where is the Mainframe technology used? …
- Expand DRDA. …
- What are the disadvantages of Mainframe technology? …
- What is SPOOL? …
- What is the difference between supercomputers and mainframes? …
- Expand SPUFI. …
- Expand QMF.
What is a bolt dispute in mainframe?
Why you choose mainframe?
