Chapter 12. COBOL

11.5Other Differences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243

11.5.1Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243

11.5.2Installation Exits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243

11.5.3Accounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

11.6References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

11.6.1PSF/VSE Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

11.6.2PSF/MVS Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

11.6.3Redbooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

11.6.4Other Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

11.6.5Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

11.6.6Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

Part 3. Converting VSE Languages to OS/390 Languages . . . . . . . . . . . . . . . . . . 247

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249

12.1Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249

12.1.1

General Comments on COBOL for OS/390 and VM

249

12.1.2

Comparison of IBM COBOL Compilers

250

12.2 VSE to OS/390 Migration Considerations

250

12.2.1Migrating Object Code . . . . . . . . . . . . . . . . . . . . . . . . . . 251

12.2.2Useful Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

12.3Converting from DOS/VS COBOL . . . . . . . . . . . . . . . . . . . . . . 252

12.3.1DOS/VS COBOL CICS Programs . . . . . . . . . . . . . . . . . . . . 252

12.3.2DOS/VS COBOL Programs Containing REPORT WRITER

Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

12.4DOS/VS COBOL and COBOL for OS/390 and VM Language Differences 253

12.4.1Common COBOL Coding Problems . . . . . . . . . . . . . . . . . . . 253

12.4.2ENVIRONMENT DIVISION . . . . . . . . . . . . . . . . . . . . . . . . . 255

12.4.3

DATA DIVISION - FILE DESCRIPTION (FD)

256

12.4.4

PROCEDURE DIVISION - Input/Output

256

12.4.5File Handling Considerations . . . . . . . . . . . . . . . . . . . . . . 257

12.5Converting from VS COBOL II . . . . . . . . . . . . . . . . . . . . . . . . . 258

12.5.1VS COBOL II CICS Programs . . . . . . . . . . . . . . . . . . . . . . 259

12.6 Converting from COBOL for VSE/ESA . . . . . . . . . . . . . . . . . . . . 259

12.7Some Conversion Considerations for all VSE COBOL Compilers . . . . 259

12.7.1VSAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

12.7.2DISPLAY Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

12.8Compiler Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260

12.8.1RES/NORES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260

12.9Reserved Words . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

12.9.1Reserved Word Considerations for DOS/VS COBOL . . . . . . . . . 263

12.9.2Reserved Word Considerations for VS COBOL II and COBOL for

VSE/ESA

265

12.10 Compiling and Running Your Converted COBOL Programs

265

Chapter 13. Assembler

267

13.1Assembler Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

13.2 General Assembler Conversion Comments . . . . . . . . . . . . . . . . 267

13.2.1System Interface and Macros . . . . . . . . . . . . . . . . . . . . . . 268

13.2.2Multitasking Macros . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283

13.2.3Interrupt Handling Routines . . . . . . . . . . . . . . . . . . . . . . . 287

13.2.4Virtual Storage Macros . . . . . . . . . . . . . . . . . . . . . . . . . . 289

13.2.5VSAM Macros . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290

13.2.6Data Management Macros . . . . . . . . . . . . . . . . . . . . . . . . 292

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IBM manual Part 3. Converting VSE Languages to OS/390 Languages, Data Division File Description FD, Vse/Esa

OS/390 specifications

IBM OS/390, a versatile operating system, was a cornerstone in enterprise environments and played a pivotal role in mainframe computing. Released in the mid-1990s, OS/390 combined the strengths of IBM's MVS (Multiple Virtual Storage) with new features and enhancements, targeting scalability, reliability, and performance in demanding business applications.

One of the key features of OS/390 was its robust support for multiple users and processes. The system allowed thousands of concurrent users to access applications and data, ensuring high availability and minimizing downtime—a critical requirement for many large organizations. This scalability was supported through various enhancements in memory management and processor scheduling, enabling optimal resource allocation across diverse workloads.

OS/390 was known for its superior workload management capabilities. The Workload Manager (WLM) component allowed administrators to define service policies, specifying how system resources would be allocated according to the priority of tasks. This ensured that critical business processes received the necessary resources while less critical tasks were managed more flexibly.

Another significant characteristic of OS/390 was its commitment to security. The operating system provided comprehensive security features, including user authentication, data encryption, and auditing capabilities. This focus on security was vital for organizations handling sensitive data, ensuring compliance with regulations and safeguarding against unauthorized access.

OS/390 also supported advanced technologies that facilitated integration and development. The system included features like the IBM CICS (Customer Information Control System) for transaction processing and IMS (Information Management System) for database management. These technologies allowed organizations to build robust, high-performance applications tailored to specific business needs.

The ease of network integration was another strength of OS/390. With the advent of the Internet and global connectivity, OS/390 systems could easily interface with various network protocols, enabling businesses to operate in a connected world. This inclusion paved the way for many organizations to expand their capabilities and offer new services, driving digital transformation.

In conclusion, IBM OS/390 represented a significant advancement in mainframe technology, combining scalability, security, and robust workload management. Its rich feature set and support for critical enterprise applications solidified its role as a vital component of many organizations' IT infrastructures, ensuring they could meet their operational challenges head-on while supporting future growth. As technology continues to evolve, the legacy of OS/390 remains influential in the realm of computing.