work, cataloged temporary, handoff, backup, transmit, master sequential, master VSAM, and so on. File classification is a large JCL-related task done to define the life cycle of all of the data sets. This task does not have a high degree of difficulty but typically involves thousands of files. Each file must be classified and this can be very time consuming.

∙OS/390 JCL Generation

JCL includes, JCL procedures and inline JCL streams are generated according to standards defined for the new OS/390 environment:

∙File Migration

VSE data file attributes (record length, label, and so on) collected during VSE JCL conversion are combined with OS/390 data file attributes determined during OS/390 JCL generation, to generate VSE and OS/390 JCL streams used to migrate VSE files to OS/390.

Each step produces a number of error and warning messages which are systematically reviewed using specific CORTEX MS statistical analysis tools.

32.5.3 Phase 4: Initial Trial Conversion

The first mass conversion is the Initial Trial Conversion and occurs before custom modification of the mass conversion tools. It is used for analysis, rather than for generating OS/390 application material. The following mass conversions are trial mass conversions, which deliver OS/390 test application material with an increasing quality, as project and conversion tool customization progress. The first trial conversion, and all following trial conversions, simulate the actual, that is, the final, mass conversion.

The initial conversion is a conversion of a small, but representative, subset of your VSE applications, usually involving at least part of your most important work. This trial conversion lets the conversion team practice a conversion and verify their understanding of the conversion tool. The first test is different and takes longer than all the others. It may take two weeks. The last conversion may take a day. The first is the longest because more problems are discovered. Problems encountered during the first trial conversion are used to identify and document additional conversion tool′s modification requirements. The conversion tool′s custom modification is refined accordingly.

The subsequent conversions, called trial conversions go on for approximately six months with a conversion being performed every three weeks. It is an iterative process throughout the six months. Trial conversions deliver OS/390 programs, load modules, JCL streams, and files for regression test in the OS/390 environment.

In trial conversions the conversion tool has been customized, the first supply is taken and the JCL and the programs are converted. The next step is to look at it and see if it worked. Is the outcome what was expected? This is initial testing. This is the testing that occurs before the teams are brought in. Many problems can be expected at this stage.

Mass conversions require several JES2 initiators and are CPU intensive. They are submitted, as much as possible, at night or during weekends in order to avoid conflicting with daily operations if any other operations are sharing the same OS/390 system.

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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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