We are also using the AS/400 for ADSM, glad to see we aren't the only ones.
Using the Work with Devices doesn't work in version 2 of ADSM.  It will not
let you save the config because it doesn't understand what a 3570 is.

Here's what I finally got to work using the command line.  We have the B11
model, I'm not sure if there would be any differences in the setup.  We also
had many problems with IP and device information on the 3570.  I have a
extensive list of PTF's that we needed to make it work if you run into the
same problems.  I would be happy to send them to you.  I remember how
frustrating it was getting help from ADSM when it came to the AS/400.

/* Library and Drive Definitions                                     */
/*-------------------------------------------------------------------*/
DEFINE LIBRARY TAPLIB02 LIBTYPE=AS400MLB MLD=TAPLIB02 CATEGORY=DSMTAPES1
DEFINE LIBRARY MANLIB LIBTYPE=MANUAL DRIVESELECTION=AUTOMATIC
DEFINE DRIVE MANLIB TAP01 DEVICE=TAP01 SHARE=N
/*-------------------------------------------------------------------*/
/* Device Class Definitions                                          */
/*-------------------------------------------------------------------*/
DEFINE DEVCLASS 3570_TAPECLASS1 DEVTYPE=3570 FORMAT=3570 LIBRARY=TAPLIB02
MOUNTLIMIT=1 ESTCAPACITY=5G
DEFINE DEVCLASS QIC_TAPECLASS1 DEVTYPE=QIC FORMAT=2000 LIBRARY=MANLIB
MOUNTLIMIT=1 ESTCAPACITY=2400M
/*-------------------------------------------------------------------*/
/* Storage Pool Definitions                                          */
/*-------------------------------------------------------------------*/
DEFINE STGPOOL 3570_TAPEPOOL1 3570_TAPECLASS1 POOLTYPE=PRIMARY MAXSCRATCH=5
DEFINE STGPOOL QIC_TAPEPOOL1 QIC_TAPECLASS1 POOLTYPE=PRIMARY MAXSCRATCH=0