State Diagram

When the Data Transfer Session begins the Tape Drive can be in two states: DOWN or UP. If it's in DOWN state then will wait until the drive receives a desired state to put it UP, passing first through the PROBING state. If it fails to put the Drive UP the system will put back the drive in DOWN state.

When it gets a mount then will pass to the state of STARTING and will call the Tape Write or Read Single Thread. Then it starts the MOUNTING of a tape and the TRANSFERRING of the data will start. After the data TRANSFERRING is finished the drive will start a CLEANING_UP, for that process it has to be done an UNLOADING and an UNMOUNTING of the tape, then the system will pass to UP or DOWN if during the data transfer session a signal to put the drive down is received. Also if after UNMOUNTING the tape the drive is still reading, the system will trigger a DRAINING_TO_DISK.