VSE 2.1 for the EXEC statement), or change the program¢s logic to read and process a ²control record² which would supply any variable information to the program.

Additional programming changes and considerations can be found in their respective programming chapters and in the POWER-JES2 differences chapter. The Cortex Migration System can provide conversion assistance in many of the areas where VSE-OS/390 incompatibilities exist.

32.5.1.2Common VSE Coding Practices Causing Conversion Problems

The following are some common VSE program coding ²practices² that won¢ t work in OS/390, and since they are mostly logic errors, won¢t be ²picked-up² nor notated by a conversion tool.

∙In COBOL, referencing a file¢s (or printer¢s) I/O area before the file (or printer) is OPENed. This will result in a system 0C4 abend in OS/390.

∙In COBOL, referencing a file¢s (or printer¢s) I/O area after the file (or printer) is CLOSEd. This will result in a system 0C4 abend in OS/390.

∙In COBOL, ²STOP RUN² statements should not be embedded within SORT procedures. These should be removed from all SORT procedures; that is, sorts must end before a STOP RUN can be requested.

∙

∙

Not OPENing a unit record file will work in VSE, but abend in OS/390.

In Assembler, using other than registers 2 through 12 for application purposes. (Registers 0, 1, 13, 14, and 15 are used for special purposes by OS/390.)

32.5.2 JCL Conversion

Mass conversions use the following steps for JCL conversion.

∙Conversion

The file information extracted during program conversion and associated data such as VSE disk and tape catalog data, is used by the conversion tool to generate individual job stream flow charts. This is done on a job by job basis.

∙Integration

The job stream flow charts are consolidated enterprise-wide to separate the application data flows (several independent data flows may use the same VSE label and even the same VSE disk space, but they become separate data sets in OS/390).

In the Cortex tool a function called file integration automates the classification of files and jobs. It also prepares reports that help determine if a file requires manual intervention. The information needing to be understood for these files and jobs includes:

-Where does the file or job reside?

-Is it permanent or temporary?

-Where does it come from?

-Where does it go to?

∙File classification

Based on data flow patterns and other functional attributes (organization, record length, and so on) files are classified according to their life cycle:

504VSE to OS/390 Migration Workbook

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IBM OS/390 manual JCL Conversion, Common VSE Coding Practices Causing Conversion Problems
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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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