Bill McEwen, from IBM Storage Systems in Tucson, came to talk about the changes in HSM in release 1.4 of DFSMS. Every time I've heard these guys talk about HSM in all its grisly detail, I remember a quote by Steve Samson from earlier in the week:

"Anyone here who has never been bitten by HSM?"
[one person raises his hand]
"You don't run HSM!"

HSM now implements VSAM record level sharing for the control dataset. But this doesn't have any noticeable benefit unless you have more than three systems sharing a CDS. We'll pass.

HSM has finally invented duplex tape, where backups are taken two copies at a time, one for off-site storage. "The other guys do 5, 15, whatever" Bill grinned. "Well now, we can do two."

You can set the maximum utilization for a backup tape; 95% seems to be the generally agreed-upon figure. (But here's something hokey: when using a 3590 Magstar emulating a 3490E, you have to specify a huge number - 1175%.) This is good for tape copies, because you can ensure that tape copies can always fit within a single volume. ABARS tapes can now be stacked - more than one dataset can be put on a volume. It's about time!

And you can finally stack dump tapes as of the new release. But all dumps on a single tape volume must expire simultaneously. Restore operations support high-speed positioning.

HSM recall does something smart. It holds a tape for five seconds after a recall is complete, waiting for another recall from the same volume.