Channels in RMAN perform all the tasks involving I/O, that is, backup, restore, and recover. Each channel will be responsible for the I/O stream that's going to either read from the disk while doing a backup or write to the disk while performing a restore. To make things easier, if you are taking a backup on the disk, RMAN configures a channel with the device type configured as disk by default. In addition to this, a default channel is also configured for maintenance-related commands such as
CHANGE, and so on. Let's see the nexus of the channels with RMAN via a figure:
In the previous figure, we have two channels: ...