Dynamic Reconfiguration General Description

The DR feature allows 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 of 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 terminates the system's ability to use any of the components on the board. Before removing a board, the DR subsystem determines whether the components on the board are being used. Removing a device that is being used would result in system errors. If the DR subsystem finds that a device is in use, this subsystem rejects the DR remove-board operation. Therefore, it is always safe to issue a DR remove-board operation.

The DR add-board operation is always safe also. 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 in order to actively use other 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 will report "Unknown error." System administrators should ignore the "Unknown error" reported by the upper level.

The following sections describe DR considerations for the different device types.