Direct access storage device interface

Offset	Bytes in Length	Field Name	Description
0(0)	4	DCBRELAD, DCBDCBE	For partitioned data sets: DCBRELAD is TTRN (beginning address) of a member. If the DCBHIAR bits at DCB offset 32 both are on, this word points to the DCBE. If the DCBE exists, and the data set is partitioned, member address is in DCBERELA in the DCBE.
4(4)	1	DCBKEYCN	Keyed block overhead.
5(5)	8	DCBFDAD	Direct access address.
16(10)	1	DCBKEYLE	Key length of the data set.
17(11)	1	DCBDEVT	Device type.
		0010 ....	Class of device. This code means DASD
		.... xxxx	Type of DASD. Programs that do not test this byte run in more environments. If a program tests this byte, it is best to test only the first four bits (class).
18(12)	2	DCBTRBAL	Current track balance. For TRKCALC macro. Not recommended for arithmetic calculation.