create or replace procedure gather_bucket_stats(p_owner varchar2, p_bucket number)
is
begin
	for t in (select table_name from (
			select table_name, ntile(8) over (order by table_name) bucket
			from dba_tables where owner = p_owner) where bucket = p_bucket)
	loop
		dbms_stats.gather_table_stats(p_owner, t.table_name, cascade => true,
			method_opt => 'for all columns size 254');
	end loop;
end;
/

show errors

create or replace procedure gather_schema_stats(p_owner varchar2)
is
	jobno number;
	what varchar2(100);
begin
	for i in 1 .. 8 loop

		what := 'gather_bucket_stats(p_owner, ' || i || ');';

		dbms_job.submit(jobno, what);

	end loop;

	commit;
end;
/

show errors