SQL> create table t
  2  (
  3    c1 int,
  4    c2 int,
  5    c3 int
  6  ) segment creation immediate;

Table created.

SQL>
SQL> alter table t memoptimize for write;

Table altered.

SQL>
SQL> select pool, sum(bytes)
  2  from v$sgastat
  3  group by pool;

POOL           SUM(BYTES)
-------------- ----------
               5771359184
shared pool     854805032
large pool       40108008
in-memory pool  536870912
streams pool     33554432

SQL>
SQL> insert /*+ memoptimize_write */ into t
  2  select rownum, rownum, rownum
  3  from dual connect by level <= 100;

100 rows created.

SQL>
SQL> select pool, sum(bytes)
  2  from v$sgastat
  3  group by pool;

POOL           SUM(BYTES)
-------------- ----------
               3489657808
shared pool     854997560
large pool     2321808760
in-memory pool  536870912
streams pool     33554432

SQL> select * from V$MEMOPTIMIZE_WRITE_AREA;

TOTAL_SIZE USED_SPACE FREE_SPACE NUM_WRITES NUM_WRITERS     CON_ID
---------- ---------- ---------- ---------- ----------- ----------
2154823680    1212896 2153610784          0           1          3