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

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:

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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 27