redo log generation during unrecoverable/nologging

# Capture amount of redo logs generated when table is created in UNRECOVERABLE
SQL> select vs.name, vm.value
from v$mystat vm, v$statname vs
where vm.statistic# = vs.statistic#
and vs.name like '%redo size%';

NAME VALUE
—————————————————————- ———-
redo size 597736

SQL> create table test_all unrecoverable as (select * from all_objects);

Table created.

SQL> select vs.name, vm.value
from v$mystat vm, v$statname vs
where vm.statistic# = vs.statistic#
and vs.name like '%redo size%';

NAME VALUE
—————————————————————- ———-
redo size 648936

CREATE TABLE with NOLOGGING option
SQL> select vs.name, vm.value
from v$mystat vm, v$statname vs
where vm.statistic# = vs.statistic#
and vs.name like '%redo size%';

NAME VALUE
—————————————————————- ———-
redo size 1193320

SQL> create table test_all nologging as (select * from all_objects);

Table created.

SQL> select vs.name, vm.value
from v$mystat vm, v$statname vs
where vm.statistic# = vs.statistic#
and vs.name like '%redo size%';

NAME VALUE
—————————————————————- ———-
redo size 1244436

Amount of redo logs generated for CREATE TABLE AS
– without UNRECOVERABLE/NOLOGGING option = 478904
– UNRECOVERABLE option = 51200
– NOLOGGING option = 51116
The amount of redo size is considerable less when nologging/unrecoverable is used.
Note: The database has to be in ARCHIVELOG mode to see the difference, if the database is in NOARCHIVELOG mode you won't see the difference.

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