1.6 How can I configure a tape drive, say LDEV 8, for AUTOREPLY?

:SYSGEN

SYSGEN>IO
IO>MDEV 8 MODE=AUTOREPLY
IO>HOLD
IO>EXIT
SYSGEN>KEEP
SYSGEN>EXIT

Now do a SHUTDOWN, followed by a START NORECOVERY and the tape will be AUTOREPLY.

Note: As of MPE/iX 5.5, you should be able to do this online in two steps by using the IOCONFIG utility to first delete the drive and then add it back in with AUTOREPLY enabled. Not a good idea though unless you absolutely can not do a START NORECOVERY. This is because the change will not be present should you do a START RECOVERY at some later date before having done a START NORECOVERY.