Device: IBM 3390 disk (56,664 bytes per track, 15 tracks per cylinder). With SMS, coding BLKSIZE=0 or leaving it out lets the system pick the best size.
Best BLKSIZE for your record length and the space a file needs on 3390.
Device: IBM 3390 disk (56,664 bytes per track, 15 tracks per cylinder). With SMS, coding BLKSIZE=0 or leaving it out lets the system pick the best size.