I don't want to do a restore nor I can do a restore. Anyway. The way to remove all disks instead of disable OC was the way I'm looking for.
I had one bootable 10.14 Install disk and one seperate disk where I want to install 10.14 which I connect both at the front USB ports. Before I remove all disks I bless the 10.14 bootable install disk via startupvolume then shutdown the MacPro5,1 and remove all bootable disks and connect the two disks via USB front.
After the machine starts and the chime sounds it took a short time until the machine finds the blessed 10.14 bootable installer disk and begin to boot. The rest was easy going.
Thank's for the hint about to remove the disks... I was not aware of this trick.
I had one bootable 10.14 Install disk and one seperate disk where I want to install 10.14 which I connect both at the front USB ports. Before I remove all disks I bless the 10.14 bootable install disk via startupvolume then shutdown the MacPro5,1 and remove all bootable disks and connect the two disks via USB front.
After the machine starts and the chime sounds it took a short time until the machine finds the blessed 10.14 bootable installer disk and begin to boot. The rest was easy going.
Thank's for the hint about to remove the disks... I was not aware of this trick.