32.6.1.1 Converting the Development Material

This is the code that the systems programmers are working on. It is recommended that the conversion of these materials take place as early as possible. This conversion is not normally done at switchover time. It is not production material.

This task generally coincides with the transfer of a significant number of application developers to the OS/390 platform. Development under CMS or VSE can continue to a point. Convert the work in progress and then move the people to OS/390. This can occur three months before switchover all at once or be moved in a staged approach each week. How these are moved depends on the amount of development activity in progress, what stage of development it is in, how much growth is happening and what machine resources are available. Converting these materials and personnel to OS/390 before switchover also provides extra experience in the environment.

32.6.2 Phase 6: Actual Conversion and Switchover

The actual conversion is the final mass conversion, starting with a final fresh supply of the entire conversion inventory. Both actual conversion and switchover are performed within two to four weeks, with the actual conversion starting on a Monday, and the switchover being completed on a Sunday. Production testing is used to validate the actual conversion before switchover. A final supply of conversion inventory, a few days before switchover, is used to identify any late VSE change control and to carry it over to the converted OS/390 application.

As opposed to trial conversions, the actual conversion is followed by a mass migration of all permanent VSE production data files and databases to OS/390, which requires a short production outage during the weekend (typically on early Saturday morning). After the file migration, some (mostly weekend) jobs are executed and some online applications are started and verified in actual production mode.

During the month preceding the switchover, all parties participate in planning and preparation activities. These activities produce the final file and database migration JCL streams and switchover task lists.

The actual conversion and switchover are complete when the scheduled production jobs and online applications have run successfully in the OS/390 environment.

The key elements of preparing for the actual conversion are:

Final JCL Conversion Final Program Conversion

32.6.2.1 Final JCL Conversion

A key task associated with the final JCL conversion is freezing the production database. The actual JCL conversion should be done as late as possible before the switchover, but before the final program conversion.

Another key task is performing the known manual changes to the production database. At this point, the production database is established in a final form, so further modifications made to jobsets during VSE production must also be made to the conversion tool production database. Implement a change control

516VSE to OS/390 Migration Workbook

Page 540
Image 540
IBM OS/390 manual Phase 6 Actual Conversion and Switchover, Converting the Development Material, Final JCL Conversion

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.