Data control block—BPAM, BSAM, QSAM

Offset	Bytes in Length	Field Name	Description
20(14)	4	DCBBUFCB	Address of buffer pool control block.
20(14)	1	DCBBUFNO	Number of buffers required for this data set. Can range from 0 to 255. Default = 1 for PDSEs; various defaults
21(15)	3	DCBBUFCA	Address of buffer pool control block. If the low-order bit is 1, this field does not point to a buffer pool.
24(18)	2	DCBBUFL	Length of buffer. Can range from 0 to 32760 bytes. Is based on BLKSIZE.
32(20)	1	DCBHIAR
		0... .0..	No DCBE, no HIARCHY
		1... .0..	No DCBE, HIARCHY=1
		0... .1..	No DCBE, HIARCHY=0
		1... .1..	DCBDCBE points to DCBE, no HIARCHY
32(20)	1	DCBBFALN	Buffer alignment:
			Code
		.... ..xx	Reserved bits.
		.... ..10	D Doubleword boundary.
		.... ..01	F Fullword not a doubleword boundary, coded in the DCB macro.
32(20)	1	DCBBFTEK	Buffering technique:
			Code
		.xxx ....	Reserved bits.
		.100 ....	S Simple buffering.
		.110 ....	A QSAM locate mode processing of spanned records: OPEN is to construct a record area if it automatically builds buffers.
		.010 ....	R BSAM create BDAM processing of unblocked spanned records: Software track overflow. OPEN forms a segment work area pool. However, WRITE uses a segment work area to write a record as one or more segments. BSAM input processing of unblocked spanned records with keys: Record offset processing. READ reads one record segment into the record area. The first segment of a record is preceded in the record area by the key. Subsequent segments are at an offset equal to the key length.
		.... 1...	XLRI being used to process a RECFM=DS or RECFM=DBS format tape data set (QSAM).
33(21)	3	DCBEODA	End-of-data address. Address of a user-provided routine to handle end-of-data conditions. If the low-order bit is 1, this field does not point to an end-of-data address.
36(24)	1	DCBRECFM	Record format.
			Code
		000. ....	Record format not available.
		001. ....	D Format-D record.
		10.. ...	F Fixed record length.
		01.. ....	V Variable record length.
		11.. ....	U Undefined record length.
		..1. ....	T Track overflow.
		...1 ....	B Blocked records. Cannot occur with undefined (U).
		.... 1....	S Fixed length record format: Standard blocks. (No truncated blocks or unfilled tracks are embedded in the data set.) Variable length record format: Spanned records.
		.... .10.	A ISO/ANSI control character at the beginning of each record.
		.... .01.	M Machine control character at the beginning of each record.
		.... .00.	No control character.
		.... ...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 those of the DCBMACR field in the foundation segment before OPEN.
50(32)	2	DCBMACR (Before OPEN)	Major macros and various options associated with them. Used by the open routine to determine access method.
			Code
		Byte 1	BSAM—Input
		00.. ....	Always zero for BSAM.
		..1. ....	R READ
		.... .1..	P POINT (which implies NOTE).
		.... ..1.	C CNTRL
		...x x..x	Reserved.
51(33)		Byte 2	BSAM—Output
		00.. ....	Always zero for BSAM.
		..1. ....	W WRITE
		.... 1...	L Load mode BSAM (create direct data set).
		.... .1..	P POINT
		.... ..1.	C CNTRL
		.... ...1	BSAM create BDAM processing of unblocked spanned records, with BFTEK=R specified: The user's program has provided a segment work area pool.
		...x ....	Reserved.
50(32)		Byte 1	QSAM—Input
		0... ....	Always zero for QSAM.
		.1.. ....	G GET
		..0. ....	Always zero for QSAM.
		...1 ....	M Move mode.
		.... 1...	L Locate mode.
		.... ..1.	C CNTRL
		.... ...1	D Data mode.
		.... .x..	Reserved.
51(33)		Byte 2	QSAM—Output
		0... ....	Always zero for QSAM.
		.1.. ....	P PUT
		..0. ....	Always zero for QSAM.
		...1 ....	M Move mode.
		.... 1...	L Locate mode.
		.... ..1.	C CNTRL
		.... ...1	D Data mode.
		.... .x..	Reserved.
50(32)		Byte 1	BPAM—Input
		00.. ....	Always zero for BPAM.
		..1. ....	R READ
		.... .1..	P POINT (which implies NOTE).
		...x x.xx	Reserved bits.
51(33)		Byte 2	BPAM—Output
		00.. ....	Always zero for BPAM.
		..1. ....	W WRITE
		.... .1..	P POINT (which implies NOTE).
		...x x.xx	Reserved bits.
52(34)	1	DCBOPTCD	Option codes.
			Code
		1... ....	W Write-validity check (DASD).
		.1.. ....	U Allow a data check caused by a character that is not valid. (Impact printer with UCS feature.) Write-tape-immediate mode (3480 and 3490). B Treat EOF and EOV labels as EOV labels which allows SL or AL tapes to be read out of order. (Magnetic tape.)
		..1. ....	C Chained scheduling requested.
		...1 ....	H Input Tape Files: Requests the testing for and bypassing of any embedded VSE checkpoint records found. (This code can only be specified in a JCL statement.)
		.... 1...	Q An ASCII data set is to be processed. The tape does not have to have ISO/ANSI labels.
		.... .1..	Z Magnetic tape devices: Use reduced error recovery procedure.
		.... ..1.	T BSAM and QSAM only: user totaling.
		.... ...1	J Specifies that the first data byte in the output data line will be a 3800 table reference character for dynamic selection of character sets.
57(39)	3	DCBSYNA	Address of user's synchronous error routine to be entered when a permanent error occurs. If the low-order bit is 1, this field does not point to an error routine.
62(3E)	2	DCBBLKSI	Block size.