Once I upgrade from release r11.3, does CA 7 r12.1 USERMODs need to be Reassemble/Link in r12.1?
Yes. You are required to re-assemble all usermods in release 12.1 from prior 12.0/12.1 releases. This is due to the version number change in the macro library of release 12.0 and 12.1.