IMS DB Interview Preparation Guide
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IBM Information Management System (IMS) is a joint hierarchical database and information management system with extensive transaction processing capabilities.

39 IMS DB Questions and Answers:

1 :: What is an IMS Database?

A Database is a collection of related data items organized in a way that can be processed by application programs.

2 :: What is DBMS in IMS?

A Database Management System is used to define and maintain the structure of the database.

3 :: What are the objectives of DBMS in IMS?

► Increases data independence
► Reduces data redundancy
► Provides data communication facilities
► Reduces data maintenance
► Provides data integrity and security
► Provides indexing capabilities

4 :: What is IMS (DB/DC)?

IMS (Information Management System) is IBM’s hierarchical database management system. It has mainly two components: IMS DB and IMS DC (also know as IMS TM)

IMS DB - IMS/Database Manager as the name implies manages the IMS databases. It is used for physical storage creation and management and data retrieval.

IMS DC / IMS TM - IMS/Data Communications or IMS/Transaction Manager handles online transaction processing system.

5 :: What do you mean by Hierarchical Database?

► Follows inverted tree structure
► Data relationship is predefined by it's structure
► Program accesses the data through predefined paths.

6 :: What are the advantages and disadvantages of a Hierarchical Database?

► Speed of access is faster because of the predefined data paths.

► Complex implementation
► Predefined tree structure reduces flexibility.
► Difficult to manage

7 :: What is DL/I?

DL/I is a command-level language to manipulate IMS databases. DL/I forms a bridge between application program and IMS database. It is used in batch and online programs to access data stored in IMS databases.

Every access to an IMS database is through DL/I. The DL/I interface must be called to update or read a IMS database. DL/I allows both sequential and random processing of a database.

8 :: Explain IMS Software Environment?

IMS Software Environment consists of the below five main components:
► DL/I
► DL/I Control Blocks
► Application Programs

9 :: What are the main control blocks available in IMS DB?

There are three control blocks (also known as DL/I control blocks)

► Database Description (DBD)
► Program Specification Block (PSB)
► Application Control Block (ACB)

10 :: What is DBD?

DBD (Database Definition) is used to define the physical structure of the database.

► One DBD for each database
► Created by a series of control statements - by a process called DBDGEN
► Used by DL/I whenever database is used