17.3.2 COBOL for VSE/ESA

COBOL for VSE/ESA is an LE/VSE-conforming language. If your COBOL applications are written in COBOL/VSE, they can (subject to certain restrictions) be migrated to OS/390 without change. You can transfer the compiled object code from VSE to OS/390, link-edit it with OS/390 Language Environment and run it there. This is discussed in 12.2, ªVSE to OS/390 Migration Considerationsº on page 250.

17.3.3 PL/I for VSE/ESA

Even though PL/I for VSE/ESA is an LE/VSE-conforming language, you cannot transfer your PL/I VSE compiled object code to OS/390, link-edit it and expect it to run. You must recompile it with PL/I for MVS and VM. However, PL/I VSE source code is compatible with PL/I for MVS and VM, so your PL/I VSE programs should compile under PL/I for MVS and VM without change. Refer to Chapter 15, ªPL/Iº on page333 for information on migrating your PL/I VSE applications to OS/390.

17.4 Migrating from Non-LE/VSE Run-time Environments

This section discusses some of the considerations of which you should be aware, if you are migrating to OS/390, and therefore OS/390 Language Environment, from a non-LE/VSE run-time environment.

If you are running VSE/ESA version 1 release 4 or VSE/ESA version 2, but you are not using LE/VSE, you should consider implementing LE/VSE in your VSE system, before migrating your run-time to OS/390. This may require that you also implement a new version of your language compiler. However, it may be easier to convert to a new version of compiler and run-time in the VSE environment, which is familiar to you, than to convert to a new compiler,

run-time and operating system, all at the same time. Refer to the relevant chapters in this book on migrating COBOL, C and PL/I applications to OS/390.

17.4.1 Options Mapping

Details of the mapping of options in OS/390 Language Environment, are to be found in the OS/390 Language Environment Migration Guide. Mapping of options for LE/VSE 1.4 are described in the LE/VSE Programming Reference Release 4. You can also find tables comparing the use of options in DOS PL/I, C/370, DOS/VS COBOL, or VS COBOL II, and in LE/VSE 1.4, in the LE/VSE Run-Time Migration Guide Release 4.

In general the mapping of options from these non-LE/VSE-conforming languages, as described in these tables, is the same for OS/390 Language Environment as for LE/VSE. However, if you are migrating from DOS PL/I or C/370 with LE/VSE you should also consider the information about the REPORT and ISASIZE options in Table 36 on page 355.

354VSE to OS/390 Migration Workbook

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IBM OS/390 Cobol for VSE/ESA, 17.3.3 PL/I for VSE/ESA, Migrating from Non-LE/VSE Run-time Environments, Options Mapping

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.