Mainframes Course

Main modules:

Overview on Mainframes
JCL
COBOL
DB2
VSAM
CICS

Overview on Mainframes

Mainframes are powerful computers designed for large-scale data processing and enterprise applications. They are widely used in banking, insurance, and government systems where reliability and security are crucial. Learning Mainframes helps understand how critical systems handle millions of transactions daily.

Mainframes Course Curriculum(Detailed)

Module 1: JCL (Job Control Language)

JCL is the backbone of mainframe operations. It tells the operating system what to do, how to do it, and which resources to use when executing batch jobs. This module covers every key concept of JCL from syntax to utilities.

Introduction

This topic introduces JCL and its role in automating batch jobs. You’ll learn how JCL controls program execution and manages system resources efficiently.

Syntax

Explains the structure of JCL statements including the use of identifiers, parameters, and delimiters. Proper syntax ensures smooth job execution.

JCL Statements

Covers the main statements in JCL such as JOB, EXEC, and DD. These define job identity, execution steps, and dataset handling.

Positional Parameters and Keyword Parameters

You’ll learn how parameters are used to control JCL behavior. Positional parameters follow a strict order, while keyword parameters can appear anywhere in the statement.

Exec Statements

Teaches how to use EXEC statements to call and execute programs or procedures within a job.

Key Parameters

Introduces essential EXEC parameters such as PGM, COND, and PARM that define how jobs and steps are executed.

PS File and PDS File Creation

Explains how to create Physical Sequential (PS) and Partitioned Data Set (PDS) files, which are commonly used in mainframe environments.

DD Statements

Covers Data Definition (DD) statements that describe the datasets a program will use during job execution.

Keyword Parameters in DD Statements

Shows how to specify attributes like space allocation, data format, and retention policies for datasets.

List of Commands

Provides an overview of useful JCL commands to monitor, edit, and control job submissions effectively.

Spool

Introduces the concept of SPOOL (Simultaneous Peripheral Operations On-Line) — temporary storage for job outputs and logs.

JCL Utilities

Learn about standard JCL utilities used for file manipulation, sorting, and data processing.

IEFBR14

A simple utility that creates or deletes datasets. Commonly used for allocating space without executing a real program.

IDCAMS

Manages VSAM datasets — defines, deletes, or modifies them efficiently through control commands.

SORT

Performs data sorting and merging operations for sequential files.

IEBGENER and IEBCOPY

Utilities used to copy, print, and create sequential or partitioned datasets.

GDG (Generation Data Group)

Explains how GDGs maintain sequential versions of datasets, useful for backups and time-based data.

Steplib, Joblib, Proclib

Covers how these libraries are used to locate and manage program executables and procedures during job execution.

Procedures

Teaches how to create reusable JCL templates to automate repetitive job steps.

Instream Procedures

Defines how to write procedures directly within JCL for one-time execution.

Catalog Procedures

Covers procedures stored in libraries and used across multiple JCL jobs for consistency and reusability.

Module 2: COBOL (Common Business-Oriented Language)

COBOL is one of the oldest and most reliable programming languages used on mainframes for business, financial, and administrative systems. This module helps you master the structure, syntax, and logic of COBOL used in real-world enterprise applications.

Background and History

Introduces the origins of COBOL, developed in the late 1950s to meet business data processing needs. It remains vital for banking, insurance, and government applications worldwide.

Structure of COBOL

Explains the organized structure of COBOL programs divided into four main divisions — Identification, Environment, Data, and Procedure — each handling specific responsibilities.

Divisions and Sections

Describes how each division contains multiple sections that group related statements, making COBOL programs modular and easy to manage.

COBOL Layout

Covers COBOL’s specific column layout and coding format, which ensures clarity, readability, and correct compilation.

Variables Declaration

Explains how variables are declared in the Data Division using level numbers and data types. Proper declarations help in memory allocation and accurate processing.

Level Numbers

Introduces level numbers like 01, 05, 77, which define data hierarchy and relationships within COBOL records.

Data Types

Covers COBOL’s main data types — numeric, alphanumeric, and computational — and their use in arithmetic and logical operations.

Compute Functions

Explains the COMPUTE statement used for mathematical calculations such as totals, averages, and other arithmetic operations.

Move and Display

Teaches how to transfer data between variables using MOVE and how to show results or messages on the console using DISPLAY.

Accept Keyword

Demonstrates how to take user input or system data (like date/time) dynamically during program execution.

Conditional Statements

Covers logical structures like IF, ELSE, and EVALUATE, which control decision-making within the program.

Files

Explains COBOL file handling methods — Sequential, Indexed, and Relative — used for reading, writing, and updating data.

Initialize and Fillers

Teaches how to reset data fields using INITIALIZE and use FILLER to reserve unused space in records.

Redefines

Shows how one data field can share the same memory as another, allowing multiple interpretations of a single record.

Perform Statements

Explains looping and control flow using PERFORM, enabling repetitive execution of code blocks or procedures.

String Manipulations

Introduces string handling techniques like concatenation, splitting, and character replacement.

Inspect Functionalities

Covers the INSPECT statement used to analyze or modify strings by counting or replacing specific characters.

Static and Dynamic Call

Teaches two methods of calling subprograms — static calls (linked at compile time) and dynamic calls (loaded at runtime).

Copybook Usage

Explains how reusable data structures are stored in copybooks for consistency and faster development across programs.

Occurs Clauses, List of Abends

Module 3: DB2 (Database 2)

DB2 is IBM’s relational database management system (RDBMS) widely used on mainframes for large-scale data storage and high-performance transaction processing. This module helps learners understand how DB2 stores, retrieves, and manages enterprise data efficiently through SQL integration with COBOL.

Background of DB2

Provides an overview of DB2’s history and purpose as a powerful database system developed by IBM to handle enterprise-level data management.

Data and Database

Introduces the fundamental concepts of data organization and database structures used to store and retrieve information logically.

Introduction to DB2

Explains DB2 architecture, components, and how it interacts with operating systems and programming languages like COBOL.

DB2 Data Objects

Covers core DB2 objects such as tables, indexes, views, and schemas that form the foundation of database operations.

DB2 Data Types

Describes various data types like INTEGER, CHAR, VARCHAR, DECIMAL, and DATE used for defining table columns.

Constraints

Explains how constraints like PRIMARY KEY, FOREIGN KEY, UNIQUE, and CHECK maintain accuracy and consistency of data.

Referential Integrity

Teaches the concept of maintaining valid relationships between tables through referential constraints, preventing orphaned data.

Indexes

Explains how indexes improve query performance by allowing faster data retrieval in large tables.

SQL Introduction

Introduces Structured Query Language (SQL) as the primary language for managing and querying DB2 databases.

SQL Categories

Describes SQL classifications — DDL (Data Definition Language), DML (Data Manipulation Language), DCL (Data Control Language), and TCL (Transaction Control Language) — and their uses.

SPUFI and DCLGEN Creation

Covers the use of SPUFI (SQL Processing Using File Input) for testing queries and DCLGEN (Declarations Generator) for creating COBOL-compatible table definitions.

Pre-compilation

Explains the process of embedding SQL in COBOL programs and how pre-compilation converts it into executable form.

Bind Process

Details how the BIND process optimizes and stores SQL statements for efficient execution within DB2 programs.

Isolation Levels

Teaches about transaction isolation levels like Repeatable Read, Read Committed, and Read Uncommitted, ensuring data consistency during concurrent access.

Cursor Concepts

Explains the use of cursors to handle multiple rows of data within embedded SQL queries in COBOL programs.

Files Concepts in DB2 Programs

Covers how external files interact with DB2 databases and how data is exchanged between flat files and DB2 tables.

Handling Null Indicators

Describes the use of NULL indicators in COBOL-DB2 programs to manage fields that may contain missing or undefined data.

Views

Explains how views are created as virtual tables from SQL queries, helping simplify complex data retrieval operations.

Subqueries

Covers how nested SQL queries extract specific data subsets and improve query flexibility.

Select Built-in Functions

Introduces DB2’s built-in SQL functions like SUM, COUNT, AVG, SUBSTR, and DATE functions for advanced data manipulation.

Table Joins

Explains INNER JOIN, LEFT JOIN, and RIGHT JOIN concepts for combining related data from multiple tables.

Different WHERE Clauses

Teaches filtering techniques using various WHERE conditions for accurate and optimized data retrieval.

SQL Codes and Abends

Lists common SQL error codes (SQLCODEs) and abend messages with troubleshooting techniques for debugging program failures.

Module 4: VSAM (Virtual Storage Access Method)

VSAM (Virtual Storage Access Method) is an advanced file storage and data management system used in mainframes. It provides efficient access, organization, and storage for large datasets, making it essential for performance-driven enterprise applications. This module focuses on the structure, creation, and usage of VSAM files in COBOL and JCL programs.

Introduction to VSAM Files

This topic introduces the concept of VSAM files and explains how they differ from traditional sequential files. It highlights how VSAM improves data retrieval speed and supports record-level access.

VSAM Dataset Types

Explains the four primary VSAM dataset types — KSDS (Key Sequenced Data Set), ESDS (Entry Sequenced Data Set), RRDS (Relative Record Data Set), and LDS (Linear Data Set) — each designed for different use cases and data structures.

Data Allocation in VSAM Files

Describes how storage space is allocated and managed for VSAM datasets. Learners understand primary and secondary extents, control intervals, and control areas for optimized performance.

How to Create VSAM Files

Teaches the step-by-step process of creating VSAM files using IDCAMS (Integrated Data Cluster Access Method Services) commands within JCL. This includes defining, cataloging, and initializing datasets.

How to Access VSAM Files in COBOL

Explains how COBOL programs interact with VSAM files through the FILE-CONTROL and DATA DIVISION sections. Students learn how to perform read, write, update, and delete operations on records.

KSDS, RRDS, LDS Files Update

Covers the techniques for maintaining and updating various VSAM file types. Students learn how to handle keys in KSDS, relative records in RRDS, and byte-oriented storage in LDS files for high efficiency.

Module 5: CICS (Customer Information Control System)

CICS is IBM’s online transaction processing (OLTP) system used on mainframes to handle multiple simultaneous user requests efficiently. This module teaches how to design, code, and manage CICS programs that support real-time data access, transaction integrity, and high-performance business processing.

Introduction to CICS

Introduces the role of CICS in enabling interactive online programs on mainframes. Students learn how CICS manages communication between terminals and applications in real time.

CICS Commands

Covers the commonly used CICS commands for program control, file handling, and data communication. Learners understand how each command ensures smooth transaction flow and data consistency.

Map and Mapset Concepts

Explains how maps define user interface screens and mapsets group related maps together. Students learn how to design and link them to COBOL programs for interactive data entry and display.

Types of BMS Maps

Describes different types of Basic Mapping Support (BMS) maps — physical, symbolic, and composite — and their role in defining screen layouts and data formats.

Program Control Commands

Teaches control commands like LINK, XCTL, RETURN, and SYNCPOINT, which handle communication and transaction sequencing between CICS programs.

File Control Commands

Explains commands such as READ, WRITE, DELETE, and REWRITE that manage file operations within CICS, ensuring safe and concurrent data access.

Map Handling Commands

Covers SEND and RECEIVE commands that manage the flow of data between terminal maps and application programs.

Task Control Commands

Introduces commands for starting, suspending, and terminating tasks. Learners understand task management and multitasking within the CICS environment.

Transient Data and Temporary Storage

Explains how transient data queues and temporary storage queues are used for storing and sharing short-lived data between tasks.

EIB (Execute Interface Block)

Describes the EIB, a control block that stores transaction-related information such as terminal ID, task number, and communication area.

COMMAREA (Communication Area)

Teaches how COMMAREA is used to pass data between programs during transaction processing, maintaining data continuity and efficiency.

HANDLE CONDITION Command , File Control in CICS ,List of CICS Abends

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