The Connect:Direct V6.4 user exit DGACXSIG uses the ACFGUCB macro to compile it's exit.
For the planning of the migration of LU18185 is this ptf backwards compatible with ACFGUCB macro from previous maintenance?
z/os ACF2
It should be fully compatible with any maint level. The ptf adds the ability to use this macro no matter how the exit is linked.
The ++HOLD instructions explain what to do.