--
-- 
alter session set db_file_multiblock_read_count = 1024
/
column value heading "Maximum possible multiblock read count"
select
  value
from
  sys.v_$parameter
where
  name = 'db_file_multiblock_read_count'
/

alter session set events '10046 trace name context forever, level 8'
/
select /*+ full(t) noparallel(t) nocache(t) */ count(*) from sys.my_source t
/
alter session set events '10046 trace name context off'
/