All locators obtained by the parameter system are annulled by ADAM at the termination of an application whether run as a single task or within a monolith. So the cumbersome process of checking the validity of locators and then annulling them can be avoided. However, it is probably neater and safer (from possible future changes in behaviour) to only assume this for locators in the top level routine of an application. All locators created in lower level routines should be properly disposed of when finished with.
All mapped data should be explicitly unmapped when no longer needed.