How does file synchronization work in between Master and Backup desk?

Hi Kelvin.  There actually isn't an show file sync required.  When you have a master/backup environment, as soon as any command is entered on a local controller -- "1 at 5 enter," that instruction is seen on both the main and backup processors.  Show file saves are stored on both the main and the backup. So, if for some reason the system transfer to backup or you transfer to backup, the show file and current stage output are maintained.   It's actually pretty elegant.  You, as the programmer, are the only person who knows, and that's because the desk tells you.