IBM¢s comprehensive testing does not replace the need for this testing in your own environment. Here are some sample steps copied from the OS/390 Checklist:

1.Initialize the system (IPL)

2.Initialize JES2

3.Log on to TSO/E

4.Run the installation verification programs (IVPs)

5.Submit a job and check its output

6.Sign on to a terminal with CICS or IMS and initialize a region

7.Submit a CICS or IMS transaction and look at the results

8.Run a complex application with known data and measure its elapsed time and resources

9.Check for completeness of accounting records

10.Test non-IBM product functions

IVP jobs are listed in your CustomPac documentation, or in OS/390 Planning for Installation. This list is not complete and should be tailored for each installation based on the importance of each function, likelihood of errors, and expanded as experience dictates.

25.5.1.2 Applying Preventive Service

You should update your OS/390 service level to a fairly current level and run through one more verification test before you switch your production over to it. This is especially true if the migration project was long, and you have not been applying maintenance on a regular schedule.

MVS Recommended Service Upgrade (MVS/RSU) is a preventive service philosophy for all OS/390 and MVS products. MVS/RSU reduces the volume of PTFs you must apply for preventive maintenance and reduces the chance of encountering a PTF in error (PE), resulting in a more stable system.

IBM recommends that you APPLY all MVS/RSU PTFs on your OS/390 system. However, the customer must make the final decision as to what service will be installed.

CustomPac offerings (that is, SystemPac, FunctionPac, ProductPac, and ServicePac) will continue to follow the current CustomPac Service philosophy based on PUT levels combined with RSU levels.

See the OS/390 Software Management Cookbook, SG24-4775.

25.5.1.3 Providing Terminal Access to the OS/390 System

You can connect the VTAM subareas in the VSE and OS/390 systems together and use cross domain resource sharing to access OS/390 applications from terminals connected to your VSE system (or vice versa). See Chapter 16

²Implementing a Subarea Network² in VTAM Network Implementation Guide, GC31-8370 for details.

See also the samples provided in IBM Network Products Implementation Guide, GG24-3649.

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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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