IBM will be removing the option of AllowUserKeyCSA(YES) in future, enforcing it to be NO..
This may impact clients as below; When getting the sub-pool (227/228/231/241) of the common area (CSA / ECSA) using each interface of GETMAIN, STORAGE OBTRAIN, and CPOOL BUILD, the protection keys 8 to 15 (User Key) cannot be used.
Release : 12.5
Component : CA Allocate DASD Space and Placement
CA Allocate is not impacted by the z/os 2.4 CSA User Key restriction.