The duplex tape option creates two identical tapes in parallel,
with one tape designated as the original and one the alternate. To
create duplex migration level 2 tapes, specify
SETSYS DUPLEX(MIGRATION(Y))
If duplexing is not desired for your migration level 2 tapes,
specify
SETSYS DUPLEX(MIGRATION(N))
The DFSMShsm default is no duplexing.