Defining the DSECTs

Control block formats and DSECTs, and Specifying a session parameter, show the DSECT fields and equated values generated by the macroinstructions. These are the DSECT-creating macroinstructions:

Table 1. DSECT—Creating macroinstructions
Control block/data area	DSECT name and operands	Appendix
ACB	IFGACB AM=VTAM[,DSECT=YES\|NO]	E
EXLST	IFGEXLST AM=VTAM[,DSECT=YES\|NO]	E
RPL	IFGRPL AM=VTAM[,DSECT=YES\|NO]	E
Device characteristics field in NIB	ISTDVCHR [DSECT=YES\|NO]	E
Processing options field in NIB	ISTDPROC [DSECT=YES\|NO]	E
Reason codes for RTNCD-FDB2-FDBK fields in RPL	ISTUSFBC	E
NIB	ISTDNIB	E
Session parameter	ISTDBIND	F
Program operator message and command header	ISTDPOHD	L
Request/response header	ISTRH	E
Buffer-list entry	ISTBLENT	E
Application-supplied dial parameters	ISTASDP	E
Access-method-support vector list	ISTAMSVL	E
Resource-information vector list	ISTRIVL	E
Application-ACB vector list	ISTVACBV	E

In coding these macroinstructions, follow these rules:

Specify AM=VTAM as an operand for IFGACB, IFGRPL, and IFGEXLST. This distinguishes these DSECTs from similar DSECTs generated for VSAM.
Code DSECT=NO as an operand if the DSECT assembler instruction is to be suppressed for IFGACB, IFGEXLST, IFGRPL, ISTDPROC, or ISTDVCHR. This allows the fields generated by these macroinstructions to be concatenated to the current CSECT or DSECT. See Example 3 in GENCB macroinstruction.
Follow the macroinstruction with a CSECT assembler instruction or another DSECT assembler instruction unless it is the last instruction before ending the program or unless the map is to be extended intentionally. (A terminal work area could be mapped following IFGRPL, for example.)
Ensure that no labels that are generated or reserved for future use are used elsewhere in the program.
Other areas of the program use the following labels. Therefore, the application program should not use them:

    ACB     DEV     NIB     RPL
    ASD     EXL     POH     RSV
    BIN     IFG     PRO     USF
    BLE     IST     RHASD