The output from hr_utility.set_location can be redirected to dbms_output. This has an upper limit of 1 Mb. Since the assignment api's generate tons of tracing ,the 1 Mb can not be enough.

In that case, you can redirect your tracing to Oracle trace files.

Hr_Utility.set_trace_options(UPPER( 'trace_dest:trace_file'));
Hr_Utility.trace_on;