You can dynamically add, remove, and move physical I/O devices and slots to and from running logical partitions using the Hardware Management Console (HMC). This allows logical partitions to share infrequently used I/O devices (such as optical disk drives).
Logical partitions can have desired or required I/O devices or slots. When you specify that an I/O device or slot is desired (or shared), this means either that the I/O device or slot is meant to be shared with other logical partitions, or that the I/O device or slot is optional. When you specify that an I/O device or slot is required (or dedicated), then you cannot activate the logical partition if the I/O device or slot is unavailable or in use by another logical partition.