tapes don't automatically cycle

[Ayman Altounji]

I have a DLT stacker attached to an Alpha Server 4100. We are using cron to schedule backups using vdump. If the backup is small, the tape rewinds and the next tape loads correctly. However if the dump needs a second tape, the next tape does not load automatically - I thought it should. Have I missed something really obvious? The device is set to cycle tapes using the key switch on the front.