alter session set time_zone = 'Europe/Brussels'

alter session set nls_timestamp_tz_format='YYYY-MM-DD HH24:MI:SS.FF3TZH:TZM'

alter session set nls_timestamp_format='YYYY-MM-DD HH24:MI:SS.FF3'

create table tmp (  
  ts timestamp,  
  ts_tz timestamp with time zone,  
  ts_ltz timestamp with local time zone  
)

insert into tmp values (timestamp '2020-10-25 02:30:00+02:00',timestamp '2020-10-25 02:30:00+02:00',timestamp '2020-10-25 02:30:00+02:00')

insert into tmp values (timestamp '2020-10-25 02:30:00+01:00',timestamp '2020-10-25 02:30:00+01:00',timestamp '2020-10-25 02:30:00+01:00')

select to_char(ts),to_char(ts_tz),to_char(ts_ltz),to_char(ts_ltz,'YYYY-MM-DD HH24:MI:SS.FF3 TZR TZD') from tmp