DEC MicroVAX 3100 Owner's Manual page 48

If the tape cartridge cannot be inserted into the TZ30, move the
cartridge lever to the lock position. Now move the cartridge lever back
to the unlock position and reinsert the cartridge. Do not push the tape
cartridge into the TZ30 while moving the cartridge lever between the
lock and unlock positions. Otherwise the TZ30 interprets this as an
insertion of the tape cartridge.
3. The green LED will light.
4. Move the cartridge lever to the lock position to lock the tape cartridge in
the drive. The green LED turns off and the yellow LED begins to blink,
indicating that the tape is loading. When the tape is loaded (ready for
use), the yellow LED stays on steadily. Whenever the yellow LED is on
steadily and the green LED remains off, the tape is ready to use.
If the write protect switch on the cartridge is in the protected position, the
orange write protect LED is on and you will be unable to write data to
the tape.
If
you move the write protect switch to the write enable position
during operation, the system software does not recognize the fact that the
tape is no longer write protected. You must reload the tape cartridge again
before the system software recognizes the cartridge as write enabled.
Similarly, if you move the write protect switch from the write enabled
position to the write protected position during operation, the tape is
not actually write protected until the operating system dismounts and
remounts the tape.
When the yellow LED is on steadily, you can proceed with your operation.
For example, you may boot your operating system, or possibly, back up files
onto the TZ30. See your system documentation for instructions for these
and other operations.
When the tape drive is reading, writing, or rewinding a tape cartridge, the
yellow LED blinks rapidly.
If errors occur during an operation, all three LEDs blink. The green
LED will blink if a faulty tape cartridge is inserted. If this occurs, see
Section 3.1.2.5.
Learning About Your System 3-7