manner. That is, not concurrent with OS/390 and/or VM/ESA. This has lead users to ponder whether VSE is a viable and strategic S/390 operating system. This lack of confidence has forced these users to look at OS/390 as a more stable and strategic operating system with a viable long term outlook. An outlook that often catches the eye of upper I/S management and spurs the move toward OS/390. The introduction of VSE/ESAs exploitation of the ESA/390 platform however has alleviated some of this doubt. It is fair to say that the focus for VSE/ESA is support for the entry to medium sized enterprises. With this in mind, it is reasonable to not expect the full array of functionality and support with VSE/ESA that one would expect with OS/390. OS/390 will continue to focus on the intermediate-large to very large leading-edgeenvironments.

1.3 Functional Reasons for Migrating to OS/390

Besides some of the traditional reasons discussed in the previous section, there also exist some functional or other practical reasons for migrating to OS/390. While there are probably other functional reasons for migrating, this section will cover those that are typically the most common. Particularly, those that relate to applications and systems management.

1.3.1 Applications Availability

The backbone and primary purpose of any information system is its applications. This software, often considered mission critical, justifies the whole existence of information systems. Mission critical applications are those applications that are seen as most vital and crucial to the running of any business. The choice of application software is driven by business requirements. The hardware and software platforms required to support a given application is a secondary decision. Thus VSE users may find that the choice of a particular application may require the installation of another hardware and/or software platform. They may also consider a complete migration to this other software platform. Some S/390 business applications may only support OS/390. These applications may take advantage of some of the unique characteristics of OS/390 and/or its subsystems such as CICS Transaction Server, DB/2 or CICSPlex System Manager. A set of applications requiring a full function (level 2) message queuing manager, as provided by MQSeries for OS/390, is another example of OS/390 unique application capabilities.

With the announcement of Open Edition support in OS/390 a whole new set of application functions are now available to the S/390 user. Specifically, applications that were formally only available on UNIX type platforms are now available to the S/390 user. Applications such as Lotus Domino, PeopleSoft, SAP and full function Web serving bring additional application capability to the S/390 platform under OS/390.

1.3.2 Systems Management

Some of the traditional OS/390 strengths of high availability, systems management, performance, scalability and capacity have also been great attractions for the VSE user. OS/390 provides management capabilities that allow the system to more effectively manage the workload over those capabilities provided by VSE. Facilities such as OS/390 performance groups and the Workload manager provide this greater workload management flexibility.

10VSE to OS/390 Migration Workbook

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IBM manual Functional Reasons for Migrating to OS/390, Applications Availability, Systems Management

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.