Data Management Installation/Dynamic Exits

This topic discusses how installation-written exit modules can:

Take control before and after DADSM processing.
Take control during open for a DCB.
Recover from errors that can occur during the opening, closing, or handling of an end-of-volume condition for a data set associated with the user's task.
Bypass, limit, or override system-calculated values that assist you in selecting optimum DASD data set block size or control interval size.
Alter messages sent to 3480, 3490, and 3590 tape operators.

You can substitute your own exit routines for the data management replaceable modules listed in Table 1.

Table 1. Data Management Replaceable Modules
Module Name	Description	When Available
IFG0EX0B	DCB open installation exit	At open
IFG0199I	Data management abend installation exit	Open, close, end-of-volume abnormal conditions
IGBDCSX1 IGBDCSX2	Precalculation and postcalculation exit	DASD calculation services
IGGDARU3	DADSM RENAME postprocessing exit	Before exit from RENAME
IGGDASU3	DADSM SCRATCH postprocessing exit	Before exit from SCRATCH
IGXMSGEX	Message display exit	Before end of tape cartridge message display processing

The data management replaceable modules you replace must be named the same as the IBM-supplied modules. In general, the module you replace must:

Handle multiple requests (be reentrant).
Reside in SYS1.LPALIB (or be link-edited into LINKLIB).
Save and restore registers.

You can also add an exit routine for the data management dynamic exits listed in Table 2.

Table 2. Data Management Dynamic Exits
Module Name	Description	When Available
IGGPRE00_EXIT IGGPOST0_EXIT	DADSM pre-processing and post-processing dynamic exit routine. The system will add IGGPRE00 and IGGPOST0 as an exit routine to their respective dynamic exit.	DADSM create, extend, scratch, partial release and rename functions

Other products can impact the modifications you install. For example, RACF®, a component of the Security Server for z/OS, takes control at the same time as some of the installation exits. They could compete for resources.