Data control block—BDAM

Offset	Bytes in Length	Field Name	Description
16(10)	1	DCBKEYLE	Key length.
17(11)	3	DCBREL	Maximum number of tracks or blocks based on the amount of space allocated for this data set.
20(14)	1	DCBBUFNO	Number of buffers required for this data set. Can range from 0 to 255.
21(15)	3	DCBBUFCA	Address of buffer pool control block or of dynamic buffer pool control block.
24(18)	2	DCBBUFL	Length of buffer. Can range from 0 to 32760.
32(20)	1	DCBBFALN	Buffer alignment:
		.... ..10	Doubleword boundary.
		.... ..01	Fullword not a doubleword boundary, coded in the DCB macro.
		.... ..11	Fullword not a doubleword boundary, coded in the DD statement.
		.x.x x...	Reserved bits.
32(20)	1	DCBBFTEK	Buffering technique.
			Code
		..1. ....	R Unblocked spanned records: Variable spanned record format. Open forms a segment work area pool. The number of segment work areas is determined by DCBBUFNO. WRITE uses a segment work area to write a record as one or more segments. READ uses a segment work area to read a record that was written as one or more segments.
36(24)	1	DCBRECFM	Record format.
			Code
		10.. ....	F Fixed record length.
		01.. ....	V Variable record length.
		11.. ....	U Undefined record length.
		..1. ....	T Track overflow.
		...1 ....	B Blocked (allowed only with V).
		.... 1...	S Spanned (allowed only with V).
		.... .00.	Always zeros.
		.... ...1	Key length (KEYLEN) was specified in the DCB macro. This bit is inspected by the open routine to prevent overriding a specification of KEYLEN=0 by a nonzero specification in the JFCB or data set label.
37(25)	3	DCBEXLSA	Exit list. Address of a user-provided exit list control block.
42(2A)	2	DCBMACRF	Macro reference after OPEN. Contents and meaning are the same as DCBMACR before OPEN.
50(32)	2	DCBMACR	Macro reference before OPEN: major macros and various options associated with them that will be used.
50(32)		Byte 1	Code
		00.. ....	Always zero for BDAM.
		..1. ....	R READ
		...1 ....	K Key segment with READ.
		.... 1...	I ID argument with READ.
		.... .1..	S System provides area for READ (dynamic buffering).
		.... ..1.	X Read exclusive.
		.... ...1	C CHECK macro.
51(33)		Byte 2	Code
		00.. ....	Always zero for BDAM.
		..1. ....	W WRITE
		...1 ....	K Key segment with WRITE.
		.... 1...	I ID argument with WRITE.
		.... .x..	Reserved bit.
		.... ..1.	A Add type of WRITE.
		.... ...1	Unblocked spanned records, with BFTEK=R specified and no dynamic buffering: The user's program has provided a segment work area pool.
52(34)	1	DCBOPTCD	Option codes:
			Code
		1... ....	W Write-validity check.
		.1.. ....	Track overflow.
		..1. ....	E Extended search.
		...1 ....	F Feedback.
		.... 1...	A Actual addressing.
		.... .1..	Dynamic buffering.
		.... ..1.	Read exclusive.
		.... ...1	R Relative block addressing.
56(38)	4	DCBSYNAD	Address of SYNAD (synchronous error) routine.
62(3E)	2	DCBBLKSI	Block size.
81(51)	3	DCBLIMCT	Number of tracks or number of relative blocks to be searched (extended search option).