The DR feature enables operations, such as the removal of system hardware, in running systems. The DR processes are designed to ensure continuous system operation with no need to halt the system or interrupt cluster availability.
DR operates at the board level. Therefore, a DR operation affects all the components on a board. Each board can contain multiple components, including CPUs, memory, and peripheral interfaces for disk drives, tape drives, and network connections.
Removing a board that contains active components would result in system errors. Before removing a board, the DR subsystem queries other subsystems, such as Sun Cluster, to determine whether the components on the board are being used. If the DR subsystem finds that a board is in use, the DR remove-board operation is not done. Therefore, it is always safe to issue a DR remove-board operation because the DR subsystem rejects operations on boards that contain active components.
The DR add-board operation is also always safe. CPUs and memory on a newly added board are automatically brought into service by the system. However, the system administrator must manually configure the cluster to actively use components that are on the newly added board.
The DR subsystem has several levels. If a lower level reports an error, the upper level also reports an error. However, when the lower level reports the specific error, the upper level reports Unknown error. You can safely ignore this error.
The following sections describe DR considerations for the different device types.