System Control Blocks Used by IGGPRE00_EXIT and IGGPOST0

The common IGGPRE00 and IGGPOST0 parameter list contains the addresses of system control blocks. The following table shows the mapping macros:

Mapping Macro	Control Block
DCBD	DCB¹
ICVEDT02	EDT02
IECIEXPL	DADSM pre- and postprocessing installation exit parameter list
IECPDSCB	Partial DSCB
IECSDSL1	DSCB
IEFJFCBN	JFCB¹
IEFTIOT1	TIOT¹
IEFUCBOB	UCB¹
IEZDEB	DEB¹
IHADSAB	DSAB¹
¹Only certain fields in these control blocks are intended as programming interfaces.

For create, extend, and partial release, the address of the JFCB passed to the user exit points to a copy of the real JFCB. Updating the JFCB copy does not cause a corresponding change to the real JFCB. During catalog processing, a dummy JFCB is built with minimal information and passed to DADSM for space allocation. Certain bits that are turned on in the real JFCB might not be turned on in this dummy JFCB. For a create request on an SMS-managed volume, if the pre-processing exit changes Start of change any space amount, End of change it will have no effect.

For partial release, the DCB and DEB whose addresses appear in the parameter list are created for internal DADSM processing only.

During extend processing for a VSAM data set, the exit is provided with the address of a dummy DEB. This DEB does not contain any extent information. DEBs for PDSEs and for sequential extended-format data sets contain incomplete extent information.