A removable media device reads and writes to media (tape, CD-ROM, or DVD).
You must have either a tape or an optical (CD-ROM or DVD) device available for every logical partition. The system also uses some of these devices as the alternate restart or IPL device and alternate installation device.
Logical partitions can (depending on your hardware setup) share a tape or optical device and its attaching IOP among themselves. However, only one logical partition can use the device at any time. To switch devices between partitions, you must move the IOP, with the shared device, to the desired logical partition. For more information on how to move an IOP, refer to Logical Partition concept IOP.
The media in the device is what the system uses to start from when you perform a D source IPL. The alternate IPL device loads the Licensed Internal Code contained on the removable media instead of the code on the load source. It may also install the system.