Data control block extension (DCBE)

A DCBE is defined by a DCBE macro and mapped by an IHADCBE macro.

Offset	Length or Bit Pattern	Field Name	Description
0(0)		DCBE	DSECT name.
0(0)	4	DCBEID	DCBE eyecatcher ‘DCBE’
4(4)	2	DCBELEN	Length of DCBE. Minimum value is 56. The current level of the system ignores fields beyond that offset; however, future levels may use those fields.
6(6)	2		Reserved.
8(4)	4	DCBEDCB	DCB address. Set by system. Must be zero when OPEN is issued. Set to zero at CLOSE.
12(C)	4	DCBERELA	Partitioned data set — address (in the form TTRN) of member currently used.
16(10)	1	DCBEFLG1	Flags set by system.
	1... ....	DCBEOPEN	DCBE has been successfully opened.
	.1.. ....	DCBEMD31	System allows user to call access method in 31-bit mode and, if QSAM, system will honor DCBEBU31. Set by system before DCB OPEN exit.
	..1. ....	DCBESLBI	In DCB OPEN exit routine: the system will support large block interface (LBI) if requested. After DCB OPEN exit routine: the user requested LBI (by turning on DCBEULBI) and OPEN set this bit on before the DCB OPEN exit. In this case, DCBEBLKSI contains a valid value and the user must not use DCBBLKSI.
16(10)	1	DCBEFLG1	Flags set by system..
	...1 ....	DCBE_32BIT_INUSE	Device using 32-bit block numbers might be due to CAPACITYMODE=XCAP
17(10)	1	DCBEFLG2	Flags set by user.
	.... ..1.	DCBE_REQST_XCAP	CAPACITYMODE=XCAP. Extended capacity. Device to use 32-bit block identifiers if supported.
17(11)	1	DCBEFLG2	Flags set by user.
	1... ....	DCBEBU31	RMODE31=BUFF. QSAM buffers may be above 16 MB line and CLOSE will free them. System may test this during concatenation. This will be ignored for BSAM and user supplied buffers.
	.1.. ....	DCBENEOD	PASTEOD=YES. The system's indicator of the end of the data set is to be ignored on input for striped data sets.
	...1 ....	DCBENVER	NOVER=YES. OPEN is to bypass the verification of consistent stripes of a striped data set.
	.... 1...	DCBEGSIZ	GETSIZE=YES. OPEN is to calculate the size of the data set (RBNs) and store this number in DCBESIZE and DCBEXSIZ.
	.... .1..	DCBEULBI	User requests large block interface (LBI). Before OPEN calls the DCB OPEN exit routine, a 1 means that DCBEBLKSI is valid and might be 0.
	..x. ..xx		Reserved bits.
18(12)	2	DCBENSTR	Number of stripes for a striped data set. Zero if data set is not striped. Set by OPEN or when switching between data sets in a concatenation. Set before OPEN or EOV exit is called.
20(14)	8		Reserved.
20(14)	1	DCBEFLAG3	Flags set by user.
	1... ....	DCBELARGE	Indicates whether the application program can handle the interface for large format data sets. 1 means yes and 0 means no.
	.1.. ....	DCBEBFXU	FIXED=USER. Indicates no I/O pagefixing needed. User is responsible for passing fixed buffers.
	..1. ....	DCBEEADSCBOK	EADSCB=OK. Indicates users supports 28-bit cylinder DSCBs.
	.... .001	DCBESYNC_SYSTEM	SYNC=SYSTEM
	.... .111	DCBESYNC_NONE	SYNC_NONE. 000 means SYNC is not specified. Combinations of these three bits other than 000, 001 and 111 are reserved.
	...x x...		Reserved.
	xxxx x...		Reserved.
28(1C)	4	DCBEBLKSI	BLKSIZE coded on DCBE macro or, if BLKSIZE=0 was coded, value set by OPEN. After OPEN, this field is valid only if OPEN set DCBESLBI on.
32(20)	8	DCBEXSIZ	Number of blocks in current data set. Set by system when DCBEGSIZ is set.
32(20)	4	DCBESIZO	High order word of DCBEXSIZ.
36(24)	4	DCBESIZE	Number of blocks in current data set. Set by system when DCBEGSIZ is set.
40(28)	4	DCBEEODA	Address of user provided end-of-data routine. May reside above or below the line. Used instead of DCBEODAD. Will be zero if no address is given.
44(2C)	4	DCBESYNA	Address of user provided SYNAD routine. May reside above or below the line. Used instead of DCBSYNAD. Will be zero if no address is given.
48(30)	6		Reserved.
54(36)	1	DCBEMACC	MULTACC. Accumulation number multiplier.
55(37)	1	DCBEMSDN	MULTSDN. Multiplier of system determined NCP.
56(38)		DCBEMINL	Minimal length of DCBE in any release.
56(38)		DCBEEND	End of DCBE. This label is always after the last DCBE field.