IBM Power System 9040-MR9 Manual page 84

Figure 71. Partially sliding the system into the rack
c) Using the connector labels near the ends of the SAS cables, attach the SAS cables to the rear of
the disk drive backplane as shown in the following figure.
Hold the disk drive backplane while you attach the SAS cables to prevent the disk drive backplane
from tipping forwards out of the system.
70 Power Systems: System backplane