Table 41 (Page 2 of 2). ILC Migration Considerations

To Migrate:

You Need To:

 

 

 

A phase containing one or more VS

1.

Upgrade the C/370 source code, and

COBOL II programs, with calls to or from

 

compile with OS/390 C/C++ .

C/370

2.

Transfer the VS COBOL II object

 

 

code to OS/390.

 

3.

Link-edit the load module with

 

 

OS/390 Language Environment.

 

 

 

17.4.8 Migrating Assembler Applications

The Assembler distributed with OS/390 is the High Level Assembler for MVS & VM & VSE (HLASM). Therefore, this is the same product as the high level Assembler distributed with VSE/ESA. If you are using the old VSE Assembler, you will first have to convert your assembler programs to HLASM. You can use HLASM on VSE/ESA version 1 release 2 or later.

To use HLASM with LE/VSE or OS/390 Language Environment, you need to code the applications with the assembler macros provided with LE/VSE or OS/390 Language Environment. You must also ensure that the assembler programs adhere to certain conventions for register and storage usage, for condition handling and accessing input parameters. For example, you should avoid using register 12 because Language Environment uses that register when establishing the execution environment for the application.

For more information see the chapter on assembler considerations and Language Environment macros in the OS/390 Language Environment Programming Guide. You should also read Chapter 13, ªAssemblerº on page 267.

17.5 Migrating from LE/VSE

This section discusses some issues you should consider when migrating from LE/VSE-conforming languages and LE/VSE.

The items discussed here are only some of those you should consider; they are items for which the behavior in OS/390 Language Environment is different from their behavior in LE/VSE. You should also read the migration guides for OS/390 Language Environment, and for your release of LE/VSE.

17.5.1 Run-time Options

In general the run-time options with OS/390 Language Environment have the same usage and the same default values as the corresponding options in LE/VSE.

However, there are some considerations of which you should be aware when planning your migration.

The following options have different behavior in OS/390 Language Environment to their behavior in LE/VSE.

Chapter 17. Language Environment (LE) 359

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IBM OS/390 Migrating Assembler Applications, Migrating from LE/VSE, Run-time Options, 2 of 2. ILC Migration Considerations

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.