Using AP and DR Together

Dynamic Reconfiguration (DR) and Alternate Pathing (AP) are designed to work closely together. DR enables you to attach and detach system boards without halting the operating system, as described in the Sun Enterprise 10000 Dynamic Reconfiguration User's Guide. AP enables you to switch usage away from a controller on a board that is being detached or possibly to a controller on a board that has been attached.

On the Sun Enterprise 10000 server, AP automatically switches each disk and network metadevice that has an active controller on a board being detached (assuming a viable alternate path exists on another board). Also, on the Sun Enterprise 10000 server, AP prevents you from manually switching to controllers on a board that is in the drain state of a DR detach operation.

The following AP command shows that the pln1 controller is on a board that is detached (as indicated by the DE flag) and, thus, you cannot switch to that controller:

# apconfig -S

c1      pln0  P A
c2      pln1  DE  
        metadiskname(s):
                mc1t5d0   
                mc1t4d0   
                mc1t3d0   
                mc1t2d0   
                mc1t1d0 

Similarly, the following AP command shows that the pln1 controller is on a board that is in the drain state (as indicated by the DR flag) and, thus, you cannot switch to that controller:

# apconfig -S

c1      pln0  P A
c2      pln1  DR 
        metadiskname(s):
                mc1t5d0   
                mc1t4d0   
                mc1t3d0   
                mc1t2d0   
                mc1t1d0 

AP is notified that a board is in the DR drain state only on the Sun Enterprise 10000 server.

When you plan to detach a board that hosts the active controller of a pathgroup, you can manually switch to a controller on another board before the DR detach operation, or even during the DR detach operation. On machines other than the Sun Enterprise 10000 server, however, you must perform any such switch before you enter the Complete Detach state, or the detach operation will fail. In this case, you can perform the switch and then retry the detach operation.

For more information about DR, see the Sun Enterprise 10000 Dynamic Reconfiguration User's Guide.