∙tailoring and custom modifying the conversion tools through installation options and exit routines according to the conversion specifications

∙performing a pilot conversion of a subset of the conversion inventory after having custom modified the conversion tools

∙auditing the messages and OS/390 material (source code and JCL) produced by the pilot conversion

∙performing technical tests on a representative sample

The Custom Modification phase is complete when the conversion process automatically handles the conversion requirements as defined during the Specifications phase.

Two additional items are associated with the objective of Custom Modifications. They are:

∙

∙

Manually modifying some code for the areas where the tool will not be used

Positioning the VSE source to remove incompatibilities

VSE Positioning

VSE Positioning is about modifying the VSE code to eliminate VSE to OS/390 conversion requirements that cannot be automated.

The positioning which doesn′t impact the logic of the code, can be applied by hired consultants. The positioning which impacts the logic of the code (misplaced stop runs, access to file buffers before open or after close, and so on), is best left to application support personnel familiar with the code.

In any case, the positioned VSE code is then regression tested under VSE by application support personnel and rolled back into production under VSE. It is collected later on for conversion, together with the rest of the application inventory.

Manual OS/390 Conversion

The objective of manual conversion is to complete the automated conversion process by applying manual modifications to the OS/390 version of the code, when fully automating the conversion is too complex or is not cost effective, and when VSE positioning is also impossible.

Manual conversion activities may be required for the conversion of

VSE-dependent Assembler programs, part of the COBOL to COBOL for OS/390 conversion, and a few low occurrence JCL conversion issues.

Manually converted elements are subjected to a one time automatic conversion to take into account all the conversion requirements that can be automated. Then they are set apart from the automated conversion process. They are repetitively supplied with the rest of the application inventory for mass conversion. Instead of being re-converted each time, they are only source compared (source compare utility program) to the version manually modified, in order to identify the latest VSE version changes, if any, and duplicate them manually in the OS/390 version.

Because such activity is in contradiction with the mass, automated and repetitive conversion approach, it is kept to a minimum number of application items that

502VSE to OS/390 Migration Workbook

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IBM manual VSE Positioning, Manual OS/390 Conversion
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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.
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