How to change column identify from sequence to GENERATED ALWAYS with data - oracle

Question

as my title, I want to change my identity column by sequence to GENERATED ALWAYS.
For ex, I have a table like this:
CREATE SEQUENCE DPT.Deposit_SEQ
START WITH 1
INCREMENT BY 10
NOCACHE
NOCYCLE;
CREATE TABLE DPT.TEST(
Id NUMBER(10)DEFAULT DPT.Deposit_SEQ.nextval NOT NULL
,Code VARCHAR2(20),
CONSTRAINT PK_TEST PRIMARY KEY (ID)
);
Insert into DPT.TEST (ID, CODE) values (1,'ABC');
COMMIT;
Now, I want to change from sequence to GENERATED ALWAYS like this:
Id NUMBER(10) GENERATED ALWAYS AS IDENTITY START WITH 6
INCREMENT BY 10
NOCACHE
NOCYCLE;
I tried by create one more column and drop old column but failed. How can I do that?
Thanks!

Answer 1

"But failed" is not an Oracle error and is difficult to debug.
Anyway, it works for me:
Create table and a sequence, insert some rows:
SQL> CREATE SEQUENCE Deposit_SEQ START WITH 1 INCREMENT BY 10 NOCACHE NOCYCLE;
Sequence created.
SQL> CREATE TABLE TEST
2 (
3 Id NUMBER (10) DEFAULT Deposit_SEQ.NEXTVAL NOT NULL,
4 Code VARCHAR2 (20),
5 CONSTRAINT PK_TEST PRIMARY KEY (ID)
6 );
Table created.
SQL>
SQL> INSERT INTO TEST (ID, CODE)
2 VALUES (1, 'ABC');
1 row created.
SQL> INSERT INTO TEST (ID, CODE)
2 VALUES (3, 'DEF');
1 row created.
SQL> SELECT * FROM test;
ID CODE
---------- --------------------
1 ABC
3 DEF
Drop current primary key column (ID) and add a new, identity column:
SQL> ALTER TABLE test
2 DROP COLUMN id;
Table altered.
SQL> ALTER TABLE test
2 ADD id NUMBER GENERATED ALWAYS AS IDENTITY START WITH 6;
Table altered.
SQL> SELECT * FROM test;
CODE ID
-------------------- ----------
ABC 6
DEF 7
SQL> ALTER TABLE test ADD CONSTRAINT pk_test PRIMARY KEY (id);
Table altered.
SQL>
As you can see, no problem.