The process and duration to migrate from PCF to ICSF depend on your installation. You can use different modes in different stages of migration. To change modes, change the COMPAT option in the installation options data set and restart ICSF. When you complete migration to ICSF, you can run in noncompatibility mode to use the full function of ICSF.
When you first install an ICSF system, you can continue to run PCF for production and just test ICSF. Because you are running the products separately but simultaneously on the same z/OS system, you can run in noncompatibility or coexistence mode. To run in compatibility mode, you need more than one z/OS system. You can run the test applications on ICSF on one z/OS system while you run your production on PCF on another z/OS system.
When you begin testing ICSF, you can run existing applications in either compatibility mode or coexistence mode to test the PCF macros on ICSF. After you run the test applications, you may want to bring up production using PCF applications on ICSF. When you bring over PCF applications to ICSF, you can run in coexistence mode. In this mode, you can run an application on PCF and then reassemble the application to run the application on ICSF.
While, or after, you bring PCF applications into production on ICSF, you can run test applications that call ICSF services. You can then convert the applications that call PCF macros to applications that call the ICSF services. The ICSF services provide enhanced key separation, performance, and function. After you convert all your PCF applications to ICSF applications, you can activate noncompatibility mode and have the full function of ICSF.