5.Security

6.Performance

7.Capacity Planning

8.Testing

9.Backup/Recovery

10.Disaster Planning

11.Project Plan Development

2.5Approaches to Migration

2.5.1 Disclaimer

For the purpose of providing a more effective guide the mass migration method was adopted as an approach or strategy in migrating. The reasons for the choice are numerous, but they include:

Mass migration provides a project duration that is definable. This allows for a more accurate migration project cost estimation and sizing.

In today¢s integrated I/T environments it is more difficult to define discrete kernels. For example, many applications currently have integrated facilities that support the integrated nature of many business functions. This can be found in applications such as Enterprise Resource Planning (ERP). The sales forecasting function, for example, shares information with certain accounting functions. This makes it difficult to separate or define discrete kernels to migrate.

2.5.2 OS/390 Conversion and Production Implementation Strategies

There are two different strategies (or approaches) you can use in migrating applications to OS/390. They are: (1.) the kernel/progressive approach, and (2.) the single switchover - mass application migration approach. The decision as to which approach to take will have a definite impact on the project, particularly on the manner in which resources are deployed Additionally, the approach decision will, in most cases, have the greatest impact on sizing the project. The following discussion presents these two approaches.

2.5.2.1 Kernel/Progressive Approach

Here, an installation defines discrete application sets called kernels 2. The conversion team uses progressive conversions of each defined kernel, placing a converted kernel into OS/390 production on a ²when ready,² serial basis. After a kernel is cutover3 to OS/390 production, the next defined kernel is worked on, converted, and implemented on OS/390. This process goes on until all applications (kernels) are cutover to the OS/390 environment. Some points to make about the ²kernel approach²:

2A kernel is usually defined as all the programs and files that are needed to support a business application; for example, the payroll system.

3 ²Cutover² is a term generally associated with the kernel approach. It is a word used to describe the completed conversion of a kernel to OS/390; that is, the time when the kernel is placed in OS/390 production.

Chapter 2. Sizing the Effort

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IBM OS/390 manual Approaches to Migration Disclaimer, Kernel/Progressive Approach

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.