IBM® recommends that you become comfortable with distributed mode before exploiting the ability of distributed mode to define more than 99 MCS, SMCS and subsystem consoles in a sysplex. Defining more than 99 MCS, SMCS and subsystem consoles in a sysplex can greatly complicate a fallback, should one be necessary. You should defer defining additional MCS, SMCS and subsystem consoles in the sysplex until you are comfortable that you will not need to fallback.
If you have taken advantage of the ability to define more than 99 MCS, SMCS and subsystem consoles in a sysplex, you will lose some number of your MCS, SMCS and subsystem consoles when you fallback to shared mode. The way in which you have distributed the consoles in the sysplex will determine which consoles you will retain and which consoles you will lose when you fallback, since only the first 99 MCS, SMCS and subsystem consoles that are defined within the sysplex will survive. You should avoid configuring large numbers of consoles on the first systems that join the sysplex because doing so may result in only a subset of your systems having consoles. z/OS® does not require that every system in a sysplex have a console. Properly configured, any console in the sysplex can see messages from and send commands to any system in the sysplex. Each system will always have a system console available through the hardware management console (HMC) that can be used as the "console of last resort" should a fallback become necessary. The DISPLAY CONSOLES,SHAREDMODE command can be used to show the MCS, SMCS and subsystem consoles that will survive a fallback.
EMCS consoles are unaffected by a fallback.