|Interesting, I was told that 4mm DAT tapes don't support variable
|record lengths.

DATs can run in fixed or variable-length record mode. (I've always
run mine variable.) One thing I've wondered is whether there is
any difference between the on-tape representation of an n-byte
recored written in variable mode and a record written in fixed mode
with an n-byte block size.

|All I know is that once I tried to install DECnet/E
|using a TZ30 drive (half height SCSI TK50) rather than a TLZ06 (4mm
|DAT) it worked.

I once tried to install Ultrix on a Microvax from a DAT. The initial
boot went ok but then it checked and refused to load the distribution...

Dan Lanciani