InterSystems FAQ rubric
There is no need to recompile the routines after the version upgrade, but since the version update overwrites %SYS, user-created INT and OBJ format routines (*.INT,*.OBJ) in %SYS will be deleted. Therefore, you need to be careful.
MAC, INT and OBJ routines with the following names are not deleted.
%Z*.INT, %z*.INT, Z*.INT,z*.INT
%Z*.OBJ, %z*.OBJ, Z*.OBJ,z*.OBJ
Please note that classes/CSPs need to be compiled after upgrading.