The format of the MODCB macro used to modify an exit list is:

The subparameters of the MODCB macro can be expressed as absolute numeric expressions, as character strings, as codes, as expressions that generate valid relocatable A-type address constants, in register notation, as S-type address constants, and as indirect S-type address constants. Subparameters with GENCB, MODCB, SHOWCB, and TESTCB, further defines these operand expressions.

See: z/OS DFSMS Using Data Sets for information about what determines the addressing mode and the parameter list residency mode set when the exit routine gets control.

label

specifies 1 to 8 characters that provide a symbolic address for the MODCB macro.

EXLST=address

specifies the address of the exit list to be modified. You can modify an exit list at any time—that is, before or after opening the data sets for which the list indicates exit routines. You cannot, however, add an entry to the exit list if it changes the exit list's length; the exit list must already be large enough to contain the new exit address. The order in which addresses are stored in the EXLST control block is: EODAD, SYNAD, LERAD, JRNAD, and UPAD. For example, if you generate an exit list with only the LERAD exit, you can add entries for EODAD and SYNAD later. However, you cannot add the JRNAD exit address, because doing so would increase the size of the EXLST control block. The MODCB macro does not support the UPAD user exit.

The remaining parameters represent parameters of the EXLST macro that can be modified or added to an exit list. For an explanation of these parameters, see EXLST—Generate an exit list at assembly time.

Requirement: If the JRNAD exit is changed for an OPEN ACB, then the ACB must be closed and reopened to use the modified JRNAD exit.

For more information about user exit routines, see z/OS DFSMS Using Data Sets .