1.1 Introduction 1.2 Job Entry Subsystem The decision to migrate from JES3 to JES2 can be difficult because of the following factors: Additionally, some customers face the following questions: IBM announced the JES3 withdraw after the release following the z/OS 2.4 release. IBM  remains committed to help the JES3 clients successfully migrate to JES2 and continues to  be available to field questions and help clients plan for a successful migration. Unlikely. However, required changes to maintain the current functionality of JES3 will be  done. However, functions are being delivered with JES2, such as the Spool encryption  and compression, JES2 policies, Disk Reader capability, and enhancements on JES3  JECL support on JES2. The migration should be a business decision that is based on the functions that your  organization uses. Migration to JES2 is not currently required. However, remember that  the z/OS release after z/OS 2.4 will be the last z/OS release that will include JES3. Customers are highly encouraged to use JES2 because JES3 will not be available in the  near future. IBM recommends that you avoid migrating from JES2 to JES3. Job Entry Subsystem (JES) is a required and strategic part of the z/OS operating system. Up  to the z/OS release after z/OS 2.4, IBM offers two JES choices: JES2 and JES3. In the past,  JES3 was considered to be the premium choice and continues to have license fees today. In the early days of JES2 and JES3, the differences between the two were more obvious than  they are today. JES3 was originally developed to assist installations that needed to manage  multiple IBM MVS™ images. However, JES2 is used by most z/OS customers and became  nearly a superset of JES3 functionality. Today, JES3 functions, such as multi-system consoles, automatic tape sharing, dynamic  initiators, and workload balancing, can be provided by the operating system. Therefore, they  are available to installations that run JES2. This difference has left some JES3 installations  wondering whether the premium they pay in licensing fees to run JES3 is still worthwhile. Also, with the challenges for the use of integrated technologies and digital transformation,  JES2 and JES3 must provide functionality, such as high availability, fault toleration, or digital  integration capabilities with new environments. 4  A Guide to JES3 to JES2 Migration GLYPH<SM590000> I was considering migrating from JES2 to JES3. Should I? GLYPH<SM590000> If I am new to z/OS, which JES should I use? GLYPH<SM590000> Do I need to (or should I) migrate from JES3 to JES2? GLYPH<SM590000> Will JES3 feature new functions? GLYPH<SM590000> Is JES3 going away? GLYPH<SM590000> Your organization sees few benefits in a JES2 migration. GLYPH<SM590000> High dependency on JES3 features that you cannot give up. GLYPH<SM590000> The cost of migration exceeds the reduction in license fee. GLYPH<SM590000> The current staff lacks JES2 skills.