This book provides information for organizations that have both JES3 and JES2 and would like to consolidate onto JES2. It will also be beneficial to organizations that have only JES3 and are considering migrating to JES2.

In Part 1, we cover the information that you need to make a migration decision. In Part 2, we cover the information that you need to plan your migration.

Perhaps one of your first questions is “Why would an enterprise want to convert to a different job entry subsystem”? There are a number of possible reasons why you might be considering such a move:

Not all of these apply in every case. As with any IT strategy, your decision will be based on a thorough analysis of the costs and benefits of migrating, based on the latest information.

This book helps you identify what the migration effort would be. For some JES3 installations, the migration might be relatively easy, but for others it will be time-consuming and complex. It depends on the extent to which you exploit the capabilities that are unique to JES3.

Many of the issues that need to be addressed when performing a JES3 to JES2 migration pertain to the use of facilities that, at one time, were only provided by JES3. Over time, many of these facilities were provided by the operating system. However, naturally, people continue using things that they are familiar with.

Even if you never migrate to JES2, it is a good idea to ensure that any new applications or new jobs avoid the use of facilities that are unique to a particular Job Entry Subsystem (JES). Most enterprises take a number of years to deliberate over whether they will perform the migration or not. During that time, you could potentially be creating many more things that will subsequently need to be addressed as part of the migration.

In the opinion of the authors, it is a very good investment of your time to put tools, documentation, and education in place now to ensure that your users (including operators, production schedulers, application developers, and system programmers) stop using mechanisms that are unique to JES3. If you have both JES2 and JES3 today, it is worth considering to stop using mechanisms that are unique to any JES.

6.1.1, “Positioning moves” on page 90 provides information about changes you can start making in advance of any migration. Additionally, throughout this book we point out changes that can be made now that will not impact current operations under JES3, but that will make the migration easier if you decide to go down that path in the future.

The book is divided into two parts. Part One gives you information to make your migration decision. Part Two gives you the information that you need to plan for your migration.

The next chapter provides background information about how JES2 works.