Under VSE/ESA version 1 release 4, and VSE/ESA version 2 and above, the COBOL compilers available were DOS/VS COBOL, VS COBOL II, and COBOL for VSE/ESA; CCCA/VSE is available to aid the conversion process. Now, only the COBOL for VSE/ESA product is available.

If you are running DOS/VS COBOL, you will have to convert your code to a new COBOL compiler level. Section 12.3, ªConverting from DOS/VS COBOLº on page 252 outlines the various options open to you, to convert from DOS/VS COBOL.

Section 12.5, ªConverting from VS COBOL IIº on page 258 outlines some differences between VS COBOL II and COBOL for OS/390 and VM that you need to consider when migrating to COBOL for OS/390 and VM.

12.2.1 Migrating Object Code

If you are running VS COBOL II or COBOL for VSE/ESA, it is possible to transfer your compiled object code from VSE to your OS/390 system, linkedit with OS/390 Language Environment and run it there.

If you intend to do this, there are two compiler options to consider that affect the way your program runs under OS/390. These options are DECK and OUTDD.

DECK

Use the DECK compiler option to produce an object program in a

 

format that is suitable for migration to OS/390. The object program

 

produced when the OBJECT compiler option is specified is not

 

suitable for migration from VSE to OS/390.

OUTDD

When you run a COBOL for VSE/ESA program under OS/390, the

 

OUTDD compiler option is used to specify the name of the file for

 

run-time DISPLAY output.

 

If you do not specify the OUTDD compiler option, the default is

 

SYSOUT.

You should also check that there are no migration issues that you need to consider, between Language Environment for VSE/ESA Version 1 Release 4, and the release of Language Environment running in your OS/390 system. Language Environment for VSE/ESA 1.4, is functionally equivalent to Language Environment release 1.4 under OS/390. However, the release of Language Environment running in your OS/390 system will probably be much higher than 1.4.

Appendix C of the COBOL for VSE/ESA Programming Guide has more information on migrating COBOL for VSE/ESA object programs to OS/390.

12.2.2 Useful Publications

Table 32 on page 252 lists some publications that you may find useful when planning your conversion. Even if you are planning to convert directly to COBOL for OS/390 and VM, you may still find the COBOL for VSE/ESA Migration Guide useful. Also, Taking Advantage of IBM Language Environment for VSE/ESA has some useful tips on converting DOS/VS COBOL programs that also apply when converting to COBOL for OS/390 and VM.

Chapter 12. COBOL 251

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IBM OS/390 manual Migrating Object Code, Useful Publications, Deck, Outdd, Sysout

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.