32.6.3.2 Additional Switchover Tasks

These tasks may also need to be addressed during switchover:

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RJE workstation configurations

NJE end users must change their JCL for job submission

Configuration of PC workstations

Migrate the tape manager to MVS

Migrate the database manager to MVS

Migrate the Report Manager database to MVS

Secure on-site assistance from major vendors

Preparing for switchover takes about a month. A detailed and timed switchover plan is developed. Final switchover file migration and backup procedures (VSE and OS/390 JCL streams) are developed, starting from similar procedures used during testing. The OS/390 environment (catalogs, tape manager, disk space) is cleaned up from any trace of testing. A final supply of programs and JCL is compared to the supply used for the final mass conversion. Modified VSE elements are identified and converted to OS/390 (or the VSE changes are manually applied to the OS/390 version) to bring the OS/390 applications to current VSE production level.

32.6.4 Phase 7: Initial OS/390 Operations

The objective of this task is to support initial OS/390 operations with conversion-related issues. The conversion team works with the operations team to analyze and resolve any operations exception created by the conversion of programs and JCL, or by the file migration. In particular, the conversion team systematically verifies if the exception is isolated, or if similar cases can be identified and corrected before they create new operations exceptions. Initial OS/390 operations typically require 24-hour on-site assistance during the first week. It tapers down to 12-hour on-site plus 12-hour on call during the second week, and 8-hour on-site plus 16-hour on call during the third week. The need for operations assistance by the conversion team ends three to five weeks after switchover.

After conversion, start your OS/390 system slowly. Ease into it and segment it where possible. Don′t let the job scheduler run free. Bring up one CICS region at a time. Run the first batch job and check the results before proceeding. If it is bad you can still back out. Always allow for a way to return to VSE if you have to.

The assisted MVS operations phase typically lasts three to five weeks. This phase is complete when all daily, weekly and monthly production jobs have executed successfully within the MVS environment. This also marks the end of the VSE to OS/390 migration project.

518VSE to OS/390 Migration Workbook

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IBM manual Phase 7 Initial OS/390 Operations, Additional Switchover Tasks
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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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