When you are trying to run TwinCAT in a virtual machine and getting 'Setting TwinCAT in Run Mode on shared core(s) inside VMware (virtual machine) is not possible' error message after activating the configuration, 

it is most likely because all the cores are dedicated to VM and there is no isolated core available for TwinCAT. You can check the cores by selecting Real Time and Read from target. As you see below, all of the cores are shared currently. 

Now we need to allocate at least one isolated core for TwinCAT. You can press Windows+R in Windows and type msconfig.

On the following menu, select boot tab and click on Advanced options. 

Select the processors check box and choose at least one less than the total processors that VM has to allocate isolated cores for TwinCAT. I selected 3 processors for this VM.

Do a restart. 

Now you can start the TwinCAT and do a 'Read from target' again to check if there is any isolated core available. Select the isolated core for your task and click on 'Set on target'. 

After activating the configuration, now we can see that TwinCAT runs in the VM!