The large number of inactive and non-critical or obsolete tape files is not migrated. They are either eliminated, or the VSE volumes are set aside together with a last copy of the VSE tape file catalog at switchover time.

Any automated operations product, which will be used for actual production after switchover, must be installed, loaded with data used in production mode during regression testing, not for sample unit testing, but starting with full-size application functional testing and definitely throughout simulated production testing (see regression testing below).

Designing implementation standards for an OS/390 job scheduler or report manager, and loading them with job scheduling or report management instructions, is best performed with the on-site assistance of a specialist acting as a mentor and a tutor. Such a specialist may either be provided by the vendor (part of the product licensing agreement) or hired outside for a couple of months. The basic education included in the license agreement brings some understanding of the product features and limited hands-on practice, but it doesnt replace the experience of a true specialist when it comes to full size implementation as experienced in a mass conversion from VSE to OS/390.

32.5.5 Initialization Testing

Initialization tests are performed to verify that online applications (tables, transaction programs, screens, and files) have been properly defined to CICS. Transactions are started to verify that the screens come up as expected. Initialization test scripts identify the minimum input required to get from a screen to the next one. At this level of testing, results and file updates are not verified.

This is a time to ensure the basics work. Many problems can surface here including mistakes in setting up the CICS environment. Frequently terminal definitions or file definitions need to be changed. During this process you are testing both your applications and CICS itself.

32.5.6 Unit Testing

Unit testing is the first phase of testing. Early unit testing is done using a sampling of jobs and applications. These should be a representative sample, a good mix of your jobs and applications used to expose problems. The idea behind the approach is that you will discover some problems. These early problems will be global problems that affect all your jobs and applications. You will go in and fix these problems and not rediscover these as you test other areas. If you tested everything at once, you would discover and rediscover the same errors over and over again.

An approach for testing that works in most migrations is to separate the test environments into two distinct areas. These two areas are online CICS and batch applications. Typically the online portion is tested first. The online testing is easiest because there is limited JCL conversion involved. Online testing is also unique because it is converted once and you are through with it.

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IBM OS/390 manual Initialization Testing, Unit Testing

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.