Parallel Activities, Overlapped Activities

26.3.3.5 OS/390 Guest Considerations

The considerations for defining OS/390 guests are no different from those associated with defining VSE guests. From the VM/ESA point of view, the actions taken to maximize the performance of a VSE guest, would be the same as those taken to maximize an OS/390 guest. For example, specifying resource goals is done through the SHARE directory statement. Best performance is achieved by making the guest a preferred guest (V=R, or V=F), along with dedicating as many devices as possible. Other VM level scheduler controls such as setting STORBUF, or the DSPSLICE would be modified in a similar manner for both VSE and OS/390, since from the VM point of view both are virtual machines with long running units of work.

26.3.4 Summary

In summary, use of VM/ESA as a migration tool will enable you to focus more on the migration tasks, and less on tasks associated with creating a migration environment. Since this document is concerned with migrating from VSE to OS/390, we will now turn to more specifics concerning that task.

26.4 Parallel Activities

Throughout the above stages of migration, there will be many activities overlapping with one another, not the least of which are your daily production computing workload and conversion activities. The following considerations should also be factored into your choice and design of test system, including their configuration, availability and performance characteristics.

26.4.1.1 Overlapped Activities

The number of ²test² OS/390 systems will determine what can be done simultaneously by different people, or by the same people without having to restore volumes or re-IPL.

For example, you can schedule times for the maintenance system to be used alternately by systems programmers for applying and testing maintenance, for operator training, and for testing different operating system configurations or options.

26.4.2 Synchronizing VSE Applications with OS/390 Versions

After you convert your applications to OS/390, you cannot freeze them on VSE. Any changes to the programs, JCL, data, and operating procedures in the VSE production environment must be replicated to OS/390. You need to schedule a replication or re-conversion of these applications to the OS/390 libraries after they are converted.

26.5 Building the Initial OS/390 Test System

Once you turn your initial OS/390 system over to application programmers for the real conversion activities, you need to create a second OS/390 system for testing. As part of this, you should give careful consideration to what is shared between the two OS/390 systems, and how isolated they are.

430VSE to OS/390 Migration Workbook

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.

IBM manual Parallel Activities, Synchronizing VSE Applications with OS/390 Versions

Models: OS/390